I'm playing as a Redguard dressed as an Alik'r warrior, and I had the idea of finding another Redguard, either a mercenary or a friend, and giving him a Scimitar, Hammerfell Robes and Alik'r Hood to make a another Alik'r warrior.

I know that they sometimes use the items you give them, and sometimes they don't, but is it possible to do this? Would I have to enchant the items to make them better than what they're currently using?

It would have to have a better armor rating. Followers don't pay any attention to enchantments.

Thanks!

Do a look up of your follower of choice and equip them with their class in mind. Eg: faendal is an archer mainly so keeping him in upgraded light gear is very possible and having him use an upgraded bow as well.
To maintain my follower, I only make sure he has the type of gear I want him to wear in his inventory and that its the best possible grade through smithing for my level (right now I have faendal in superior elven gear and hes using a dwarven bow). Faendal also uses a dagger if I give him the option so I only allow him a bow (personal decision but not necessary).

If using a bow follower, they will not use good arrows in conjunction with a good bow eg: a dwarven bow can be used with the default followers steel arrows, but if 'forced' to use good arrows, they will revert back to their hunting bow. They will also wear rings and necklaces.