How to make room for a taller electrical panel with a vent pipe underneath
I would go with option 5 and maybe combined with option 2. First I would get rid of the split bus panel (They are no longer legal for a reason). Second I would install a two or even three section panel. This are not sub-panels the first panel has an MCB and then the other panels are lugged from bus to bus with a full size conductor.

You will be able to find these from a wholesaler as they are not a stock item.

Good Luck.