Various good points put forward from both sides.
I'll try to lay the foundation of a possible compromise here, which may sound crazy.
Taxes can be blocked from blockaded nations, but maybe not entirely. Perhaps a percentage of the tax revenue from the blockaded nation can be blocked off completely, whether that sum ends up at the blockading nation or whether it's simply just destroyed? And maybe this percentage can be proportional to the blockaded nation's tax bracket or something along the lines? Just trying to find some middle ground here; an attempt to maybe hinder alliances' ability to simply 100/100 tax blockaded nations and move resources off them but at the same time not have too much of a negative impact on alliance tax revenue.
Let me know your thoughts people!