One thing I did to improve stealth in Piecemeal was to make it a game everyone could play. In the same way that everyone got better at combat (warriors merely got better much faster) everyone got better at stealth (rogues simply got better much faster). Thus a series of fairly free form comparative stat checks came to be a stealth system and it worked pretty well. But in the last 2 months I have been gaming pretty heavily and stealth missions have become more important to the current group. This has lead me to notice that while better, it still has much room for improvement. One thing that has cropped up is how stats play too high a role, being a stat check it often comes to the fact that a lower level non-rogue with a much higher stat will be better than a pure rogue for some time in particular stealth actions. The system also doesn't truly allow for partial results: The "Three successes to escape" or "gain 2 successes before 2 failures" etc adds some tension, but I think it could be improved.
My thought is to again mirror the combat and social conflict mechanics. Round by round those involved in stealth (or trying to be on watch) would roll to increase or lower suspicion. More importantly this would then allow luck points to enter the equation.
"attacks" and "defense" rolls would use stealth mod as a "combat bonus" and score(or lower) "suspicion" by an ability scores die. Having higher suspicion would cause penalties to future checks (much as taking physical damage causes penalties). Thus you can get in situations where a character hides with baited breath behind a door as a guard looks around.
I hope to playtest this option more and release it in the next version of piecemeal.