I've been thinking about doing that for a while actually, had the GB SDK sat on my desktop for ages but haven't gotten around to giving it a go yet.
Best part about this is if you add CGB support you don't have to bother with the second VRAM bank, you can just tweak the tints to your liking. However, you no longer have the BGP/OBP0/OBP1 registers so you'll have to do everything through the main CGB palette (in other words, fades will be different), and you'll use a different attribute bit to select the sprite palette.