First off, I'd strongly suggest not to go with DRL as a Carceri module. As far as I know (more accurately would be to say "as far I am allowed to know"), a readiness stage of Carceri is far away from handling a game with a complicateness level of the DRL. So going this route would make you working on two projects at one. That's not a best way of things to go considering severity of the current situation as it is expressed in the topic line.
Moreover, I suspect, that even if Carceri would be perfectly ready it still would not allow exact transition. I don't have to explain the things that you know thyself very well, that designing a new game using Carceri would lead to design-around-limitations-and-using-it's-features while transition of another game would require copy-behaviour-intact-no-matter-the-underlying-platform, so you most likely would have to choose to either sacrifice some of the rules of DRL or to add DRL-specific hacks and features to Carceri.
Now to the first option. On one side,
rewriting software is evil in general, but on the other, according to Jeff Lait, the hardest part in roguelikes is data entry, and all the rules and data for DRL are ready and tested. So, you can estimate how long will it take for the rewrite and look if adding these extra features would justify the time spent. Clearly, rewriting would be better in the long run, but how much more features are you going to add?
I think we can agree that DRL now is no more a testbed or a little toy, but a fullblown mature and complicated game, veiled by a misleading look of simplicity. New features can be invented and added for an infinity, but you have to put a line somewhere.
If you are going to simply add some features to the game, refactioring is the way to go, but by the phrasing of your question it's clear that you are going to start from scratch by some way. Wouldn't it be better to declare the current version DRL a finished game and declare a new game as DRL II and do not put tight restrictions of exactly reproducing it (remaking things you did once is somewhat boring and players do not care when there is no difference to see) but take a chance and make a truly new game keeping the spirit and distinctive features of the DRL.