Which is amusing, but misses the point.  I'm asking what actual procedures or aspects of the social contract prevent that from happening in the OP's group.  This is with the understanding that nothing would prevent sloth man from going into super parkour mode, given the OP's statement as such earlier.

His character concept. If his character concept is "I can shoot eye beams" and the rest of the party/DM is ok with that, then fine he can shoot eye lasers.

This is more what I was getting at; I would have thought, for example, that True Shapeshifting would only cost say -2 or 3 not the -4 it does...it doesn't to me seem to be much more powerful than Beast Change which is -1. You need Modular Abilities to pick up anything concrete rules wise, all it really allows is freedom to swap your skills around willy nilly based on your form, and I'm of the opinion that while that flexibility is potent, it's nowhere near as cool/potent as say Thaumaturgy (which could with time and effort actually outpace True Shapeshifting and a moderate score in Modular Abilities) and is certainly not as powerful as the Surernatural Speed, Strength or Toughness Abilities. I 'm not trying to be argumentative, I just trying to illustrate that the balance issues aren't always apparent to everyone.

The thing about true shapeshifting is that it means that any physical/perception abilities are always going to be used at your maximum skill level (since you can just shift them around). This is basically +2 or more to every physical and perception skill, for all trappings.

I'd allow it with a maneuver, or by spending a fate point to invoke their Red Court Vampire aspect for effect.