Bobemor, if the penalties for tax evasion are more costly than reasonable tax rates, then “opt-out” taxes would absolutely not buff or encourage solo play.
I agree that it doesn’t make sense to be able to “opt-out” out of armed conflict. I’m all for conflict. The current problem is rooted in a lack of any ability to engage in conflict. A cartel group can rule a planet and non-cartel players have no ability to resist (other than through toxic verbal conflict, which we don’t want).
A key characteristic of conflict is that it is costly to both sides, and that it is generally more costly to both sides than cooperation. If you make opting out of taxes costly enough to both sides, then opting out of taxes becomes, defacto, a means of engaging in conflict.
In that case, opting out of taxes is more than just a solution to the current useless base problem, it is essentially opting into political/economic conflict. It’s saying “You’ve pushed too far. I refuse to comply. I’m going to oppose you - even if it costs both of us.” That is realistic, especially in a ‘wild-west’ frontier where authority/enforcement is tenuous at best. Refusal to pay taxes is basically rebellion. Rebellion is the ultimate check and balance, and it is always a last resort because it is costly.