Ahoy,
in my honest opinion the best solution for the problem is to introduce some kind of upkeep-cost which increase dependent on how many flags you own.
Solves the problem with
-sleepers, this should be pretty much self-explanatory.
-greedy small companies which flagspam like there is no tomorrow.
-its also more transparent for the flag-owner. That way you can exactly see for how many hours your flag is protected. Right now - I even dont know if I have an lagacy flag or not and how active I have to be in my claim to get my flag protected again.
Btw. getting land is not that hard as some of you ppl might think. Mentioned greedy small companies are mostly unable or unwilling to defend their land properly. I got myself a nice spot in a tropical biome after "everything was claimed". On one Island I was able to attack 3 different flags successfully. One of them even on a beach which I finally took.
I can also confirm that some companies are willing to give land for free if you have a nice chatter with them.