Well flat vehicle taxing based on weight, ICE engines are taxed additionally by tax on fuel. Not all taxation needs to/should happen in a single space.

If the US raises gas prices the desire to drive gas guzzling pickups and SUVs will automatically lower (I hope).

And about paying taxes for something im not leveraging.. depending on the tax burden and possible energy saving based on reduced weight I don't know. It might just be fully impractical as a system that allows for easy swap in and out of batteries might add so much weight and complexity it makes the whole exercise pointless anyway.

I'm mostly just hoping on improvements in battery tech in general. That aging EVs can be equipped with newer batteries with higher power density.