No xp penalty, but it does prevent you from ever raising scout again without suffering xp penalties (especially since you can't raise monk again, even if you wanted to). Maybe you don't care about that, I'd find it annoyingly restrictive.
Ascetic hunter lets Ranger and monk levels stack for determining unarmed damage and also allows me to multiclass feely between the two. I would just have to raise monk before I raised scout, don't know why I would want to though. I would leave it at 1st lvl if I could avoid the xp penalty.
Let me get this straight...NPC already has you in melee, you're going to dance around to get your skirmish damage so your melee attacks actually do decent damage. Instead of using that same movement to just...I don't know...get out of melee and shoot the sucker? DC 15 Tumble is not terrifically hard. The only other scenario I can visualize where melee would come up is if you thought it would be a good idea to toss away all your feats and bow training, and all the money you poured into the bow, so that you could go in and mix it up with fisticuffs, actually seeking out melee. If I've misread your logic, please correct me.
I was simply saying that if I was going to melee why would I use a bow as a quarter staff when my fists deal more dmg and have a better to hit via weapon finesse. I am sure there will be situations(such as those small tight dungeon corridors) where I will find myself unable to use my bow very effectivly to skirmish and would simply use the melee as an alternative.