this is a good idea, and a fairly easy one to implement. do you mean
present all of the pdb files (or the like) from a chosen directory in a
list, and load each molecule via a double-click?
Yes. Exactly. Probably with the directory as a button/textelement at the top of the list? Whatever.

if you have experience coding in Xcode, plug-in development is fairly
Not really. I've never invested the time in learning how to use xcode. I hope there's also a way to do it from a vi/command line style...

In a nutshell, you use the pymol api to send pymol commands. The only
funky part i've seen so far involves bridging Python and Objective C
Used py-objC bridge before, and it was okay.