Just adding this note so nobody gets their expectations up by the first still-positive post. /Zapp
I am deeply frustrated with 4E in many respects. In order to know how to proceed I need to make clear what I like and what I want. Posting this here if anyone else has any relevant thoughts.
Please don't defend Cubicle 7. The aim of this post is to sort out my thoughts, not battle self-appointed shining knights defending C7's honour. That is, if you want to offer an alternative take on individual points, I'm willing to listen. If all you want is argue why C7 is so much better at creating rules than I am, this is not the thread for you.
Concepts I hate
Dwarves/Elves being so much better than Humans/Halflings. I don't want to have effectively level three characters in my level one party.
The idea that NPCs don't get access to the special abilities of PCs. For example: an NPC Cat Burglar should definitely be able to have the same Alley Cat Talent available to thieving PCs.
The default implementation of Advantage - what were they smoking when they decided a creature could quickly gain +100% to attacks?!
Armour crit negation, since this makes armour a must-have. This is a most unwelcome shift compared to how 1E/2E made armour "nice" but far from essential
The split between unopposed +20 Tests and opposed +0 Tests: I want to just ask my players to make a Test without having to tell them if they get +20 or not. The rule should make it the DMs internal business to decide whether a result of -1 SL is good enough and/or the Test is important enough that an opposed roll is mandated. Do note: the idea that you generally succeed even if you fail by less than 20 is reasonable. I just don't want the players to have to adjust what SL they report.
I want all kinds of characters to be able to participate in dangerous adventuring (ie combat), not just the Warriors. Being stronger, faster and more skilled is already advantage enough. Looking at NPCs, the difference between "civilians" and "soldiers" is perhaps reasonable, but when it comes to player characters they're adventurers first, and civilians or soldiers only second. I consider every edition of WFRP to fail in the way it allows some characters to use much better weapons, and get two or even three attacks; while others are stuck with hand weapons and the single attack.
Loads of special rules and exceptions in weapon qualities
Loads of special rules and exceptions in monster traits
Loads of special rules and exceptions in critical hits
The notion that spellcasters should suck and that anything more than a basic zap spell should require you to spend rounds channeling
At the same time, I also note the broken math that leads spellcasters to quickly become über-powerful even with moderate amounts of experience. Just ignore more powerful spells and instead use the basic attack spells, and spend your gobs and gobs of SLs on more damage and more opponents. You should find you can soon oneshot most encounters...
The "fantasy battle" heritage of WFRP magic sucks donkey balls. Specifically, I detest how the license forces C7 to make
* Spellcasters must be college-educated, and that there's only one set of colleges, and that they're all based in Altdorf
* A spellcaster is either an Uber-Elf or restricted to just one colour of magic
Complicated, incomplete monster stats
Bretonnia past 1st Edition
Concepts I don't like
That WS/BS now is of supreme importance, relegating Strength/Agility to secondary status
That Agility was split into Dex, Agility and Initiative with no effort to rebalance the full set of characteristics, making Dex the ultimate dump stat if you're lucky not to need Dex for your concept
Meta-concepts such as Motivations; having to come up with "short term goals" to get your points back (Bonus XP, Resolve, etc)
That having just a single +1 Advance counts as being proficient in a skill.
Lots of niggly -10's and +10's modifying everything
Lax "help other" bonuses. Players should not routinely say "I help her" and expect to get a bonus to the test. Tests are generally calibrated for the case when one hero steps up and attempts the test.
Sure, some tests assume multiple people, but that's the exception and not the rule. For instance, if you need to remove a fallen tree to be able to keep moving, the Test difficulty already from the start assumes a single character can't do it and that several people will help out. In this case, helping out bonuses are reasonable.
Absolutes. Abilities that say "you can't be surprised" or "you attack before everyone else" or "you can't be spotted" or somesuch. They need all to be replaced with a generous bonus that still allows uncertainty.
Rules that take away the GMs final authority to decide whether you succeed or fail. No rule should allow a player to point to the rulebook and say "it says here I do it, you can't tell me I can't". Believe me, I can
Advantage, a number we have to track for every PC and every NPC
A lack of easy and simple-to-remember rules governing "try again". Any time you're allowed to just try again next round, there must be a cost or risk. If there isn't there must be a limit on retries. Otherwise the action should simply be resolved as "you succeed eventually".
How some tests interact with Success Levels. (Fear, Fatigue, the list goes on) A test that requires you to get 2 SLs is not twice as difficult as a test requiring 1 SL. The much more sensible implementation is to count successes (each round you succeed means "+1") and when you reach 2 you're done.
How fear is only fearsome if the enemy comes closer
Too many combat modifiers are too large and/or too easy to come by.
Size modifications complicated and hard to remember
Encumbrance
Don't use money or encumbrance as a balance factor!
Movement. On one hand, if movement is a cost, combat becomes static and boring. On the other hand, being able to move much and still do your action before the opponent is simply too much. The nature of turn-based combat means you should get to move for free, but only a little. (If you want to make a longer or more elaborate move, that's your action for the round). If this means combat rounds can't realistically be 10 seconds long anymore, so be it.
Charging. Just downing one foe and engaging the next should not count as a charge. A charge is running towards a foe screaming.
Armour and shields too good
Dual wielding too complicated
Random risk of getting a Bleeding critical that will kill you if you don't have magic or medic (or Resolve). I dislike that the rules doesn't seem to care about the fate of hapless NPCs
That Initiative is non-random. I want every player to have at least a small chance of getting to experience their character going first, being able to set the tactics for that encounter. No player should be able to count on going 100% before the nasty monster in the corner. (At least there's ready-made options for this one)
Falling damage too realistic. Any game that wants characters to do rooftop chases need to make sure players don't avoid rooftops!
There are way too many spells basically zapping you
There are too few "interesting" or "atmospheric" or non-combat spells
The notion that counterspelling is free and effective. Counterspelling should be an interesting tactical consideration, not a wet blanket on wizard effectiveness. If you want magic users "dueling" this is not how to implement it
The lousy "game fun" value of criticals. 2E sucked because any crit above maybe 2 was too lethal (you basically always spent a Fate point if you had one). 4E sucks because there's too little differentiation between a "small" crit and a "big" crit.
Not all wizards should be assumed to be "battle wizards" trained in Weapon Skill. Not all religious careers force you into using magic, and there should be easy options for the "bookish" wizard.
Concepts I don't especially like but can live with
The 4E career framework (I loved the career network of 1/2E)
The 1 point advances
The advance XP costs
That some Talents are worthless while others are extremely good
Introducing Resilience/Resolve
Not separating between mental corruption (=insanity) and physical corruption (=mutations)
Loads of special rules and exceptions in talents
Making spellcasting into a language test
Price lists that make no sense

Concepts I like
The fact opposed tests reduce the number of combat rounds. 4E did do away with "whiffiness".
Endeavours
The social status of careers
That not all religious characters are assumed to use magic
That WFRP remains a percentage-based and skill-based game