I'd rather not have to kick out non-clanmembers every 10 minutes just to keep the % values up. At the moment, for some clans, having more troops is better than having more gold, since you need 1/3 the troops to even launch an attack, in addition having clan members also work in cities and play cRPG in general is more than enough gold.
After the population hits the cap it goes back to 100% tax rate, not a good solution.
If you want troops, buy them from the owner, it might still be 100 per troop, but it will be 100% guarantee.
The problem is, once you get a bunch of troops, what are going to do with them? Probably attack the villages you just got them all from. If you partner up with a larger clan, you may be able to get better rates on troops and maybe a few designated towns to recruit in.
2 Continents wouldn't really solve this problem, eventually all the land gets gobbled up and clans that currently don't have land, are muscled out of Strategus. But this is kind of essential, otherwise you would never be able to defeat an enemy, they would always just keep coming back, forever.
Having some benefit to having lots of people in your town/village/castle wouldn't solve much either, since the gold would just get set to 0, the clans who own the territory would still get stronger and the largest clans with the most members would rocket to the moon in strength.
There are villages out there with 25 or less taxes, you just need to find them, and don't expect anyone to tell you, because that would bring the rates down for everyone.