Best case scenario for having 5 levels of heir-looming is +5s equal the +3s of today, which is a giant middle finger to everyone except the brain dead shit-stains that love grinding for grindings sake. Worst case scenario is that the mod becomes full of weapons that, instead of simply being over-played (OP) as they are now, are actually over-powered.
If you really want to level the playing field for new players the only way to do it is a whole/partial character and loom wipe, which there is no point in doing this late in the mods life. The Warband community in general is dwindling rapidly, the game is going on 5 (6?) years now, which is just a bit to long in the current PC gaming environment for us to see any substantial growth no matter what we do to entice new players. We've got about a year and a half left (maybe 2 in Europe) before the mod dies anyhow. Not to mention Melee, M&B 2, Life is Fedual, and numerous other games that will, while not being as good as crpg in terms of combat (except melee hopefully), still zap more than a few players from this old relic of a game.
Honestly it's rather disgusting how desperate you are for an advantage over newer players. Just get better.