Is there a reason you would want to change? To my knowledge the rodi unit is just a bunch of connectors hooked up to some filters. If you wanted to change the output of your ro system, you would just need to change the ro membrane and add a new restrictor. If you want to add more pre-ro filtering it would be just adding some canisters with filters and change the line so they flow to those before the ro-memebrane (DI after).
Maybe there's more than I'm understanding, but why change the housing/plumbling for the ro/di system?