I think this would be a pretty cool planet concept to add in purely because it would add a new danger to the game. The rain would slowly damage blocks randomly generated (and those placed by the player) with stronger blocks taking longer before breaking than others. E.g: Stone takes longer to break than wood. The acid rain would also damage players but it's effects could be negated via a suit. (Such as a Hazmat suit?)
Love the idea of acid rain, especially the idea that it eats away at player-placed blocks. Higher tier metal would perhaps be immune to this. Would love a planet where acid rain means a quick death, forcing the player to wear a suit like you suggested. In a big PvP server I'd love to build here, because it would be 'natural protection' from people who don't have the suit.
To fix that why not just make it that certain parts of the terrain are immune so if you are building on the planet you must have to place the natural flora or (dirt) to protect the building therefore you plan before you build. It would be a danger to the player. Feels like it would be a good danger
The thing I'm worried about is severe server lag and the destruction of natural land. It would suck if the whole world just slowly disintegrated.
What if it only ate at player placed block? Think that was the idea - naturally generated blocks would be immune to the effects.
I like the idea, but rather than damaging blocks at different rates it might be preferable to just flag certain blocks and items acid-resistant or -immune. You really wouldn't want to be sitting in a house made of iron or an iron alloy, for example, in the middle of a sulfuric acid rain. It would be good cause to have plastic or other synthetic polymer, or ceramic, blocks.
Maybe even just weak player placed blocks like glass and dirt. That way you'd need to make some sort of shielding for your home if you have something like a wooden home.
