They don't need to keep making new heads--they just need to make ones for characters folks waited over a decade for and then got "pissed-off" heads for that don't capture the spirit of the character at all. The Merry head has been almost universally critcized, so "it is what it is" isn't going to cut it in this instance.
And who said it needed to be free? If Asmus wants to charge for it as an accessory with another figure or in an accessory pack, that's fine. In fact, it's great. I think there's enough complaints about those hobbits to sell an accessory pack with alt heads and more accessories. But if Asmus wanted to just charge an extra 10 bucks and include a head with Grisnakh, I'd be perfectly happy with that too.