Pretty cool to see someone looking at this. I did start something similar, but never finished. My goal was to commit the private key by hashing it at the end, so it couldn’t be replayed. I also commit to the current accumulator, so you can know exactly up to which height it is valid.
As already pointed out, the utreexo accumulator is dynamic and needs to be computed from all blocks. Just as a heads-up, you can use utreexod or floresta if you want to get the current roots and prove a given utxo. Furthermore, the commitment scheme used in utreexo is a bit different (I keep pondering if I should add this to rustreexo or keep it as “we only have the accumulator algorithms”).