A paintball won't even dent my safety glasses, guaranteed, i've been involved with safety glasses testing at the manufacturing stage and we use steel ball bearings for testing. It would however leave a nasty bruise on the bridge of my nose i'm sure
not to mention a splattered face.
If you're just looking to put a window in your case then it's actually very straight forward and easiest with a jigsaw, IMO:
1) tape the sidewall where you are going to cut with decent quality painters tape to minimize cut damage
2) stencil out the cut on the tape, or use template to trace it on
3) use your drill or dremel for a start cut for the jigsaw blade
4) making sure you have the correct type of blade for steel on the jigsaw cut out the hole, a jigsaw can do gradual rounded corners or big circles
5) use file to smooth out the cut
6) I use some u-tubing to cover the edge, hides minor blemishes and exposed steel which can clash with paint job if you're keeping stock finish
7) use glue or industrial 2-sided tape to apply the window, i use tape so that if i change my mind or want to make more changes later its easy to reverse.
Anyways, that's the process i use...don't know if i'm just repeating what you already know.
To cut your acrylic i think the bandsaw/sander combo is by far the best scenario, wish I had a bandsaw at my disposal, that will make your cut buddy basic.