Absolutely definitely without question you should not use the name "lightspeed Bitcoin." It's way too gimmicky and technically empty. It's like when a vacuum cleaner company says their machine has something dumb like "AccuSuck technology." When you use technically-empty marketing jargon as though it were technical language, you sound like a snake oil salesman.
If there were anything about DPOS that we're any more related to the speed of light than any other electronic technology, I'd have a different opinion.
Well, the rate at which you can send a Fast Bitcoin around the world is limited only by the speed of light and the size of the planet. You can quibble that all the routers add another second or two, but why? BTC doesn't even get close enough to where router delays are a factor.
Nevertheless, by consensus we have adopted Fast Bitcoin (FBTC) as the nearly universally preferred name.
Cool.