@fehzor
Artists would only be able to reuse code(so basically copy and paste it and change the reference to a different model, change description/name etc). They would not be able to create new behavior(cuz they're artists not programmers... New behavior requires code to be written from scratch such as defining a movement pattern of the bullets for the mixmaster so unless these artists know a decent amount of code they wouldn't do squat). That's speaking from personal expierence.
How my development process worked :
1)Use placeholders and write behaviour.
2)Get artist to switch placeholders with actual models when they're done.
3)For level design. I had an interactive interface which didn't require any code hence items which were already programmed such as gates could be placed(enemy spawn points too and you could even control certain variables of the placed objects). Changeable variables = models and stuff like that so level design is easy. Hence I just had a person dedicated to level design who just knew where thing should be placed and was creative.
So essentially the programmer would write everything that's new. And I mean literally everything. And by new I mean stuff that acts completely different to anything else in the game(ie mixmaster). Stuff like new missions and all could and should be output weekly since it's fairly easy to do so but then again. That'd be waaaaaayyy too much to ask of a development team which works 40 hours a week and gets paid for it.
Grimm
Probably a reskin of a weapon