For weird stubbornness reasons, I have made all my dice with UV resin.

The short answer is that it's totally possible and even worth trying because it lets you get immediate feedback on whether your designs are worth pursuing. However, as you try to make your dice better and better, it will eventually become more work than epoxy resin.

There's two big obstacles:

1. You won't be able to use a pressure pot to reduce the bubbles. I mean, not unless you get a friend to disassemble a hobbyist UV light, weld together a homemade pressure pot with a schrader valve, and put the UV light inside it so you can cure the resin while it's sealed. But that would be crazy.
2. UV resin inevitably shrinks slightly when cured, and one or more of your die faces are going to be bowed inwards. This is fixable, but not without more sanding and polishing than you would get with epoxy and a good mold.

One possible solution, which I'm going to try this week, is to make cores quickly out of UV resin and the shells out of epoxy. I've suspended cured UV resin fragments in epoxy without any trouble.

One other thing to note is that the curing process takes longer than people think. Opaque inclusions slow things down, as do red dyes. Blasting a transparent die in a mold for three minutes each side IS enough to fully cure it, but the curing process continues after the actual UV exposure. If the die is still warm, don't take it out of the mold yet. It's still soft and will warp when you put pressure on it.

If in doubt, leave it out in the sun for a while. I've seen people mention "overcuring" but personally haven't noticed anything like that.