One of the things that's killed me about 3.5 is how long it often takes to create characters. For 4e, it's even worse IMO.
And a lot of that I lay down on Feats and Skills (of course, it's Powers in 4e). Especially Skill Points. Sure, some of us have a pretty good grasp on what we're going for and we can knock out a non-spellcaster in less than half-an-hour. But then there are the analysis paralysis types who are going to sit there and grouse over whether they should take Cleave or Power Attack or something else for an hour or two.
Multi-classing and prestige classes (together with the build complications these create) are the other component. Because
Trailblazer removes the need for "fix" Prestige Classes, the pressure is eased. It's also simplified rolling up spell-casters.
1) Get rid of Feats. Or at least move their function into another, more freeform, less shopping-list, mechanic. Like Action Points maybe?
A serious consequence of this would be shifting time costs into the game session. My main question is: which problem are you trying to solve? It doesn't sound like you're worried about overall complexity, but rather players feeling "locked in" to their decisions.
To solve that, I recommend a two-ways solution. Firstly, go with the PHB2 solution of standard builds. These give the "not sure" player something to pick up and run with. Secondly, allow feats to be changed between adventures at no or little cost.
If those don't address the problem, then the problem is identifying what's wrong!
And how would the "+5 for Trained" model (or something similar) translate to TB? How many Trained skills would characters get? When would they get new ones?
I think skills need a more comprehensive redesign. What I would suggest is dividing what we currently think of as skills into three basic categories:
1. Things regular people do (Craft, Profession, etc.).
2. Things all adventurers do (Perception, among others)
3. Whacky things certain kinds of adventurers do (Use Magic Device, but also some high end stunts from Stealth and the like)
This is the hardest task. The conclusions from there are fairly obvious. For (1), it's better to have a non-level based skill system (i.e. no cap on skills from class level, skill points can be derived from things other than leveling). This gets around the awkwardness of 6 year old Mozart getting +8 BAB - the kid can be 0th level with a ridiculous skill in music. (2) should simply be a function of level. Things in (3) become Class Features and Feats.
I'm not sure that solves your problem, of course.
But it does remove skill points as a build complication.