I don't know if it's even possible (with SKSE, maybe?), but I've been searching the Nexus for a mod that would allow a smith/enchanter to improve/enchant your equipment (not everyone here is a smith/enchanter, you know Bethesda...??), and so far I've found nothing. Are there any mods like that? And if not, would them be doable?

It is doable when it comes to tempering, I have it implemented in a http://www.gamesas.com/topic/1467536-wip-project-ilmarinen/?p=22918605 I'm working on. Enchanting is trickier since the SKSE function that allows one to set an enchantment applies it to the base object and as such will apply the enchantment to all references of a weapon.

Tempering can be done by having the player place the items he or she wants to temper into a container that keeps track of the items. Once the player is done, then it is simply a matter of using DropObject to get an ObjectReference that SetItemHealthPercent can be called on and then give the ObjectReference to the player.