I'm working on a story called Moon Over Black Mesa. It's a Gamer Luna story where she plays Black Mesa: Source. I just posted the prologue last month, & am gonna post the next chapter when the Community Hazard Course Remake is finished.
For me, I think this is great because the MLP characters do not really fit their HL2 counterparts AT ALL. Just the opposite! XD Luna talks a lot, and loudly, whereas Freeman never does. Derpy is uncoordinated and clumsy, compared to Grigori who is a careful planner. Can't comment on Scratch since we haven't really seen her aside from fandom theories.
I don't perceive loud voice as so important to Luna character, rather, it's more like a legacy. In general, she is serious, stand-alone and introvert, which is quite what you can expect from Gordon. Also she has some class =] Grigori, on the other hand, is a little bit nuts, which plays funny with Derpy's personality. Only Derpy could have survived in Ravenholm after all!
Really? I loved that part of the game myself. The traps, the gravity gun, head crab zombies, the saw blades, the crazy priest, and the atmosphere just being some of the great things about it. Then again I find that happens a lot.