I don't get it. Lexan is very easy to machine, very forgiving. I don't see why you need a dremel tool at all. A drill (better still a drill press) and fine tooth sabre saw blade should get that done fine, then if you want to file, even sand and polish the edges, do that too. Lexan is hard enough to make that possible unlike a lot of other plastics, but even better than acrylic in not being easy to chip or crack.
The two main things not to do to lexan is try to grind it, or motorized sanding tools, either of which create too much heat. A saw usually isn't remotely close to that unless it is extremely dull.
I was cleaning up my garden cabinet the other day, and found a 1/4" x 3" (2.5) x 24" piece of so-called "hobby wood". It's poplar. I'd bought a handful of them for some minor woodworking projects, but may have thrown away the other three or four pieces.
So I've done the "fine" work of precise stenciling for the cut-out parts of the faceplate (or plates -- I'll explain). I made two blanks from the poplar, which are currently in a vise to let the glue set, bonding them back to back or doubling the width to 1/2". They are precisely cut, and just a tad larger than needed for a perfect fit in the dashboard's "plastic box".
I can fit the GAMA 3-pin LED switch and a USB port on either side of the BT06 (Chinese) MP3 player, which sits in a fitted hole. Took me some time getting the shape of that big hole to cut a precision stencil and transfer to one of the poplar pieces.
I can also cut the LEXAN the same way, but the poplar seems easier to work with. I can stain it and add a coat of polyurethane clear varnish later. The LEXAN can eventually be fitted on the front of the assembly, and the MP3 player will just exactly mate with the surface without protruding. For the moment, it protrudes 1/8" from the poplar -- or it will, when I finish the cutting.
I have some Forstner hole-cutting bits in my tool cabinet. So I can use my drill-press to cut out the material from the large hole. The small 0.5"x0.71" and similar hole for the USB port can be routed out with a Dremel cutting tool, then filed and sanded.
There will be less "inner" construction with foam-core/board than I anticipated. The dashboard's plastic box is a tapered rectangle, so the rear surface is smaller than the rectangular front hole. I'll cut three pieces of foam board to fit the back of the box, cut a 1-1/16" hole in the centers, glue them together and then fit the stacked rectangles to the female cigar-lighter port at the rear of the box. With that snug fit, the 1/2" thick poplar can be secured to the MP3 player, and it should all fit snugly.
I've tested my GAMA LED switch with the player, and completed the essential wiring to a fuse-box tap. This is going to be very neat. Seems like a lot of trouble to make an MP3 player part of the dashboard assembly, but the sound is very good, and everything works nicely.
It's gonna be cool! I hope I can eventually find the time to post a picture.