"I don't know why exactly, but a crossbow seems a lot more Quakey to me than a lightning gun. "
For me Lightning gun is the best Quake gun and also Rocket Launcher, those two just feels Quake to me.
I would love to see other enemy than shambler which uses thunder/lightning, weaker more regular enemy but with quite powerful attack. Many cases I wanted to use enemies that would change the gameplay totally, but if I really need to use shambler for that.. shambler is hard to kill, something weaker but with same attacks.
For example in Myth I : The Fallen Lords "Fetch" :
https://www.youtube.com/watch?v=17q81rwqyGg
Lightning is not fast, and is possible to dodge, but has explosion radius or something like that.