While the skill challenge mechanic has problems, I'd prefer the game to use the standard ruleset. Tweaks are okay, but don't go all Pathfinder on us (not that I have anything against Pathfinder, but I don't want to have to learn a new system for an AP).I'm certainly on board with doing things a bit differently. I'm also half on board with dumping or redesigning skill challenges.
I have one of those in my current campaignYeah it's just -4 for heavy shield + plate. If you're trained in athletics (most fighters are) and have a high Str (most fighters do) you should be around +4 to +5 at first level (16 - 18 str).
Only person I see struggling mightily is the Cha-based paladin with low Str. He could be as low as -4 at first level with 10 str.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.