2-4 of those suggestions seem fairly arbitrary and difficult to balance. If the effects of the mechanics change, it would need to be something with a dynamic. Also, your suggestion 1 would make flux management too difficult.
For example, a couple alternatives:
A. Overloading could be replaced with something more like the MechWarrior heat system, wherein you could continue operating past the flux capacity but risk internal damage and a lengthy overload period if you went too far/long over the limit. Ship performance could possibly decrease with more flux past the limit (shields would go completely offline, of course), and perhaps some ship components would change the overloading behavior.
B. Venting could act as a sort of shock absorber for energy (possibly other types) weapons, dispersing the damage while you are spewing energy everywhere. This would add a few more tactical options and increase survivability when being assaulted with high flux.