All right, so I have a suggestion for another poorly-thought-out yet far-reaching change. Aren't you thrilled?
- at each new character creation, randomly generate a large array with values between -5 and +5
- each skill check in the game is then modified by a value from this array (indexed by check sequence or whatever)
In other words, make the skill check difficulties a bit more "fuzzy", so there's some variance even in playthroughs with very similar characters. Memorizing exact skill thresholds does nothing, and the "state of the world" is always at least somewhat unknowable - it's impossible to perfectly know the depth of the pot until you've jumped in it (so to say). Each new character is in a slightly different parallel universe: in one Feng is slightly more obvious in his grubbiness but the guards are just a bit harder to bribe, while in another the opposite is true etc.
The aim is not, however, to make it more roguelike with huge variance, just to add a slight level of spice. I used 5 as the max change value since you've talked about rounding all checks to the nearest multiple of 5 (which doesn't seem to be the case in R2, judging by the changelog), but you could use <-3, 3> or whatever could be called "a slight change" based on the distribution of check values you're using (just -1, 0 or +1 would definitely be too small a change to register at all).
Yes, it could be argued that too many random changes will take away from the sense of "let's see what happens differently if I invest 5 more points in Skill X" (the all-mighty C&C). But it seems to me that if played correctly, it's more cosmetic and will just shift the choice slightly: from individual skill points (which can make or break a check, and thus reward the player for investing the exact number of points required to succeed at Quest MXI) towards "I'll put 10% of my skill points into Skill X, and see what happens this time". Or at least, that's how it looks to me.