It sounds interesting, although to be honest, I'm not a fan of how many ideas seem to be taken straight from the original Super Mario Land 2. Don't know, just... doesn't seem right for a Mario game to have about half the bosses and world concepts returning, especially not one designed like it's from the days before New Super Mario Bros became a thing.
But the levels and graphics look nice. The new ideas sound nice (such as the thunder mountain, stone piranha thing, Shy Guy villain, etc). And given how much nostalgia I still have for Super Mario Land 2 on the original Game Boy, I know I'll be trying this game out when it's actually released (even in the form of a demo).
The full game is out already, check the first post again. I only recycled bosses due to the lack of sprites, their attack patterns are entirely different in this game.