The annoying thing about RVC is that 32-bit instructions can now appear misaligned. I would be far less annoyed about RVC if it didn't break alignment, as you could solve the problem with a bunch of RVC-only decoders at the misaligned offsets.

So you either need (almost) double the number of full decoders, or a length decode and a bunch of shifters to get each decoder the right input bits (which get larger the wider the front end is. The 8th instruction can be at one of 7 possible offsets)