Yeees ... but MX keys, for example, have the stem right under the centre of the key, so any light from the LED would be much weaker in the centre, which would reduce the effectiveness of the glow on the star and sun keys in particular.
The moon would probably be the best of the three, as it kinda wraps around the centre of the key where the top of the stem would be.
I have two sets of Deck keycaps, one with larger print, and one smaller. The larger one has the legends go over the stem area port of the time. It's visibly dimmer, but still clearly visible. Since the "sun" is larger than the stem area, it'd just be a little dimmer in the very middle. I think it'd look great.
If one were putting a lot of effort into making these keycaps, you could make it less translucent in the areas around the stem, and directly above the LED, therefore making in evenly lit.
Ideally, you'd have higher powered LED's and only have a few keys be lit, that way you can up the opacity more, and get a really even lighting from it. You could have GiTD coating inside (for better lighting angles and diffusion with a reflective bottom so less light escapes out out bottom of the keycap. The keycaps itself would be either "natural" POM (Preferable) or PBT or some other plastic that is translucent. (though come to think of it, if you paint the outside, a very clear PC might be the best: Do all the diffusion with an undercoat, etc.)
There are several ways of attacking the problem, ranging from "pretty commercially (or DIY) viable" to "ludicrously difficult and expensive". Nevertheless, it can be solved.
I mean, you could even use an active material, that changes it's opacity, with a small circuit under the keycap powered by the light of a tritium capsule under it.
