Should I expand my metal band to put a custom percussionist(s)

Don't limit your band based on how you think it should be perceived. Try something new, it might just work.

>>17403804
Depends on what your sound is going to be. For a band like Slipknot, I don't feel like it is necessary for them considering their core sound is like every other nu metal band: guitars, bass, and drums.

If you have creative ideas that go beyond that style of metal music, and if you feel that custom percussion is essential for conveying your ideas effectively in a live setting, then go for it. Or you could hire live musicians like Sepultura did when they had their tribal nu metal phase. Otherwise you can just put whatever percussive sounds you want in your music while recording.

>>17403804
>>17403938
I forgot to mention the idea of using a backing track since not many people can hire live musicians. Again, it all depends on what your sound is going to be and what your goals are for your music project -- whether you want to take your band out and if your style is really dependent on custom percussive sounds.