Can be a good way to save some money, but can also cause you problems as many normal sports bags either won't be big enough for all of your kit or will not be strong enough to cope with the weight.
What I would suggest is that people look at things like Cricket bags. Most are comparable to paintball kit bags in terms of size, can carry plenty of weight, have decent wheels for if you don't feel like carrying them, and are far cheaper.
For example, right now if you want a big kitbag from Planet Eclipse then you're best option is this:
£150
34x82x36cm
However you could buy the following as an alternative:
£40
30x83x30cm
Both bags have a separate compartment at the end so you can split your kit up, but the Kookaburra bag has a large compartment at either end so you can keep muddy shoes or something away from the rest of your kit at the end of the day. Build quality is pretty much identical, size is pretty much identical, and yet the cricket bag is £110 cheaper.
It's a no brainer really.