I honestly think that if you are serious about your coin and want to streamline your coin, you need to have a lightweight wallet ready to go with your launch. When I first got in to bitcoin, I skipped the client and went straight to Multibit because I didn't want to wait an eternity for my client to sync up. Also something tells me that your grandmother will not have the patience to wait for her wallet to sync up either.
Meh. I don't think it's of utmost importance to have it ready at launch, because the blockchain will be tiny and sync almost instantly. But I do agree with you in general - there definitely needs to be lightweight clients for all the altcoins eventually. I'm not exactly sure if MultiBit is easily portable for use with other altcoins, but it's definitely a great lightweight client to use as a base.