Depending on how this is written, it could be very encompassing and not so good for other things in the industry. Want a better trigger? Nope, can't do that. Want a magazine release? Nope, no more of those either. Buffers, springs, gas blocks, etc; all potentially on the chopping block as they can affect the cyclic rate of a semi-auto firearm.
If it just specifically states 'bump stocks', fine, I'll take the hit on that even though I think it's pointless (as well as the stocks themselves) legislation. But, if it says any device capable of increasing the rate of fire, well then, I've got a big issue with that.