That's essentially how the Feudal contract worked though; nobles provided their troops but little to no tax. Cities provided money but few troops. Clergy were at some point in-between, but their loyalty was fleeting (giving money to religious head).Right now, the result is that vassals provide their "strengths" with minimal costs.
There is a choice. Take Feudal focus for example.So I get huge amounts of levies from those who provide most of the levies to begin with. I get huge amounts of gold from those who provide most of the gold to begin with.
That is NOT balanced, because there_is_no_choice.
Balance would be the reverse, so there could be some value sometimes in having those who provide gold to instead sacrifice that gold for levies, and those who provide levies to provide gold. (That doesn't happen in the current system, you ALWAYS want the default values, which, in effect, makes those values meaningless.)
You can sacrifice about 10% of your levies to get 5% tax from them; not an insignificant amount. It seems well balanced to me.
The burgher focus seems to have the wrong values currently, I'll get it fixed.
I think I need to balance the clergy values a bit better as well.