Earlier quoted context omitted.
A tax small enough to not harm indie publishers is almost tautologically unlikely to affect big publishers at all. The incentives created by fines and taxes are greatly overestimated. For something like this to work, it needs to be achievable without the continued cooperation or even existence of the original business
To the opposite, the tax should kick in if the operation is large enough. If your revenue from the game exceeds $10M, you should do some minimal continuity work. If it exceeds $100M, you should do much more serious continuity work.
I think an effective remedy for this kind of situation can't just be fiscal, we need requirements to publish adequate technical specifications and strong IP carveouts to make it likely to move the needle. Forcing companies to maintain continuous support is a non-starter. We should instead focus on enabling unofficial support from outside the companies, and remove legal threats from those who choose to do so