Full disclosure, I'm mostly responding to the OP, having only skimmed through the responses.
The last rebellion the board has seen was in June of 2018. I have only seen the Sith Empire and the CIS be bold in doing three dominions a month and complete all three of them, inviting minor factions to rebel them if they dare. Otherwise, they go free and can claim their SSD.
I don't think most people are afraid of doing more than three doms per month, but simply don't have the interest or activity for it. Currently, there's only one faction on track to complete three doms (launched in December) this month. Since the reworked map came out, there have been plenty of opportunities to launch Rebellions (Most Majors have acquired SSDs), but few have been launched.
I take it that this suggestion is part of an effort to spice up the map game, but it's probably going to have an opposite effect and just make most Majors, especially those more PvE focused, even more tepid and discourage new Majors forming.
I think the central issue with the map game isn't the lack of mechanics or avenues for PvP, but a matter of culture.
Right now, there only seems to be only two modes when it comes to Major interactions: 1) ignore or 2) beat into a bloody pulp. In the latter case, this often leads to the employment of various underhanded tactics and collusion. Whatever it takes to win. Rebellions, in particular, were reworked in part because they were being used as vehicles for Majors to troll each other and wear them down through attrition.
A lot of people invested in the map game like to treat it like they're in a real total war. This inevitably leads to toxicity between groups, and then they don't want anything to do with each other lest they (re)open that can of worms.For instance, Conquests were launched over a year ago as a low pressure means for some kind of meaningful PvP, but all Majors declined to do anything with it.
I think if Majors and other groups acted a little more chill toward each other and didn't immediately ramp up aggression to level 11, then you might see a spark of activity. We can all hate each other IC, but I don't see why we can't aim for more collaborative experiences and accept that we can't always come out on top in a story.
On our current trajectory, I just see more and more people checking out of the map game (at least PvP) and retreating to their own little islands unless we change our attitudes.