I have a block that i'd like to act as a light source, eg it still sets the blocklight of nearby blocks, keeps mobs from spawning, ice melts etc, just without visually lighting up the surroundings. Would this be possible? I'm not sure where I should start

For the mob spawning you could check when an entity joins the world (EntityJoinWorldEvent) and cancel that within a certain radius to your block. For the melting you would either use the randomtick of your block and manually melt ice around or use a tileentity for that