A roll up requires the user to control the private key of the address making signatures in order to inherit security from the chain of origin. Since the proposed design does not address incorporating BTC/ETH address user signatures, the purpose of the proposed design is to enable a canister running on the IC able to batch transactions on a chain integrated with the IC in order to overcome the tECDSA throughput limitations.
It is wonderful to see this novel proposal being developed by the community and I hope a grant is issued to support those researching this. I would suggest also integrating off-chain privately held signatures in order to make the ZKRU a true roll up which inherits the source chain’s security rather than solely using it for increasing tECDSA throughput. Direct Integration with Bitcoin - #677 by jglassemc2