For now, the transformation behind a personality trait, is fine, because, like you said, Kyle Maclachlan can stretch his range a bit, but ultimately we did to see a proper hulk-sized monster come out of this. We've been short changed too many time in comic book shows on getting to see something like that, and I really hope they don't do it again. The visual alone of him hulking out into Mr Hyde would be a huge ratings draw for the show and could turn the tide a bit.
It's not like plenty of SyFy shows haven't been able to create massive trolls, and other creatures on a much smaller budget than Marvel/Disney has for AOS. I doubt the CGI would even be that poor either, and there's also the option to just use giant prosthetics and great camera work to create the massive effect.
Let's just hope they don't make us settle for a Nolan type realistic approach in a show that Blizzard, Inhumans, Absorbing Man, Asgardians, and many other fantasy elements.