Set your estate to production and prepare yourself for regular policework. It shouldn't be that hard if you are diligent. With level 2+ walls, a unit of 100+ archers or (even better) MI should be able to manage against almost anything monsterish, unless it comes in the form of multiple units.
As for boredom, hey - people play solo strategy games all the time. Plus, people might show up to join you, you never know.
trying to make fair assumption, i mentioned that it would not be impossible that someone tries on its own, alone, but i doubt that would succeed for more than couple of days, and would not hurt anyone.
my main idea of such easing is that 3-4 players could make i-c team and have at least slight chance to form realm aside from colony takeover.
that way, those who are neither ooc gang nor part of carved-in-stone establishment would have some chance to create something new.
succeed or fail, in my view there is no difference, playing i-c is all difference.