Like any typical game, I would hope you earn the ability to expand your weapon by picking up objects (DMC 4 style with Nero - who earned more abilities by finding objects and special orbs) or finding the weapons themselves (just about any game). In a way, from an organizational point of view, you could have a single weapon that changed as you earned new abilities for it (DMC 4-ish style). I think it would be better to find individual weapons themselves. In a way, finding objects to expand Dante's abilities and weapons is nearly the same as finding individual weapons themselves. You're still having to locate and find things. The DMC series offered a good system where you could quick-switch weapons on the fly, which helped immensely with some forward planning at the start of each mission. There are two considerations to think of regarding the weapons though:
1. If NT decides to use the "expand weapon ability/morph deal" with the "alleged 18 available weapons" they better have a relatively simple and effective game play control scheme in place. Not sure about you, but I'm sure as hell not gonna even TRY to memorize 18 different combo button presses to use all the weapons in the reboot. On top of that, you gotta factor in switching to the appropriate weapon quickly and efficiently.
2. If NT uses the style/form based combat system where it's advantageous to use a particular weapon against certain enemies, NT had BETTER have a rock solid and FAST method for switching to the needed weapon quickly. From the videos, there are varieties of enemies coming at Dante all at once. So fast weapons switching better be available if this route is taken.
Personally, the Style based system of DMC 3 worked beautifully. Simple, easy, and very efficient. I hope NT uses a similar system in the reboot.