Man, I can't think of too many reasons to introduce yourself by anything other than your real name. Anything else is kind of weird to most women. I've been in this a long ass time and I've never known someone who has gotten away with introducing themselves as something that sounded like it came from a roleplaying game. Pseudonyms are for rock stars and magicians whose names are 100% congruent with their identities.
Think of it this way - the community was founded by nerds (really) who wanted to create alternate personalities online. These guys figured out some things that worked, but some of the other conventions i.e. PUA Avatars are really not what women are attracted to in the real-world... they are trends within the PUA community that caught on because some of the more outlandish thought leaders got TV shows and books. That doesn't mean they work to a guy's advantage.
Anyway, Matt and William are both great, strong, masculine names. Can a woman imagine herself with a guy named William? Absolutely. Can she imagine herself with a guy named Ambition? Hmmmm.....