Yes the game can manage semi opacity. But devs say it consume lot of ressources.
Here is an official very detailed answer about it.
I didn’t try (yet) to force semi transparency into opaque blocks.
my focus right now is to play with waterfall, because it’s a good half-working example.
I don’t know wich stance I should take about modding. The game right now is pretty open and push people like me to play a lot with the assets. Will try to make soft things first. Like gifts blocks for christmas with some candy cane gleam…rainbow garlands sparks conduits?