In general, I like something like this.
Regarding the power up tax, there might be a way to get the intended outcome without adding a persevered hurdle to powering up. For instance, all of the Hive could be powered up but the tax is collected from the tax pool drip. For instance, let’s say someone powers up 1000 Hive. They now owe 50 Hive in tax. As they get the drip, the amount they owe decreases until it reaches 0, at which point they start earning from the drip. The chain will know how much they owe so if they power down before it is collected, the tax is paid during the power down. The tax wouldn’t be avoided but it also would be as obvious either.