chracters waiting in the halls of heroes should not lvl up
Hrm, why not? I, personally, hate games where my party ends up at different levels based on who I'm using. It ends up very quickly locking you into using the exact same characters, since everyone else is too under-levelled to bother with.
i could give you sveral different reasons. i ll give you 2 for now

1. when i am playing a rolplaygame i expect my characters to be as experienced as they deserve to be, i.e. i have to earn their strenth by playing them. (roleplay argument) roleplaywhise there absolutely no excuse for that mechanic, i d even take it further and would want to have my 2 main chracters getting different amounts of exp depenting on how much they bring to the party. (damage done?, killin blows?, social achievments?, locks picked, ...)
2. having different lvls of characters in the game gives it more depth, more ways to play the game. there might actually be a reason for me to have one chracter on a lower lvl... meaning others got more exp (higher lvl) if i played them without the lower one.
to me it ends up making you figure out ways to help weaker charcters to get to lvls where they are useful...have you ever played baldurs(I) gate as mage main class? pretty fun and chalanging till you made some lvls
cheers