Lots of hypotheticals in the OP. You are assuming that PVE will have more players than PVP, but at the same time admitting that PVE would likely escalate into PVP should
any PVP resistance occur. So if everyone is ultimately doing both PVE and PVP, then the odds are that PVE pressure and PVP resistance would be roughly the same everywhere on average. So everyone is winning and everyone is losing.
Agony, you are stating a problem that is not a problem. Not even hypothetically. In fact, you make an Open-only ED sound quite fun!!!
That being said, the major flaw in your logic is that you assume that 1 hour of PVE is somehow not equivalent to -1 hour of PVE. But even if I never actually kill you, if I merely stop you from doing PVE for 1 hour, and I had to stop doing PVE for 1 hour to do it, then it's a wash. So regardless of PVE/PVP activity, it always boils down to the side with the smartest/most number of players.
In fact it's better than that for PVP though, because if you spend 1 hour collecting PVE Merits, and I log in for 5 minutes and manage to kill you before you turn them in, that's a 12:1 time advantage for PVP anti-undermining.

And my control station is only a few Ls away to turn in my kill merits and cash bounty.