Another nice feature of the LR3 is how easily it can be modified, and how many people have made some very creative mods that can provide inspiration for you to do your own mods.
One example that may be of benefit to you and your plasma build is the ability to move the belts (and belt holder, tensioner, etc), to the side of the table, and away from sparks/flame/heat. Some of those parts could also be made from aluminum. If you do that, you can also omit the stepper motor cutout from the YZ plate(s), which can act as a bit of a shield for sparks and heat.
You can also enclose the belts within unistrut, and have the rollers and rails ride on the top of the unistrut for more heat/flame proofing.
Do a search for “side mounted belts” There’s a couple of ways to do it.
One way (the most common) is to create an offset stepper motor plate that attaches to the YZ plate. (Edit - @DougJoseph has a thread that discusses this method in depth -
Here is someone who did that, and made the side plate out of aluminum as well.
Another way is to print the stepper motor side mount(s). That’s the way I did mine
If you are really talented, you may also be able to make some parts from milled aluminum, rather than printed PLA. I seem to recall someone doing that with an LR3, but I could only find examples from an LR2.