Upsides: Hull acts as if it's longer. Gain deckspace (but only the amount that the engine used to infringe on existing deckspace.)
I doubt you're going to be able to use the pod as a swim platform on your size boat (I've got a wide 18' RIB and can barely use mine that way.)
Downsides: If the boat is already tailheavy, it's going to become moreso due to the longer lever the motor has to work on. You likely won't be able to use the pod for fuel unless you install forced ventilation (at least in the US) to vent fuel vapors. You'll likely need all new control cables/hoses, and probably extensions for the engine wiring harness. You'll likely need to re-engineer any deck and bilge drains/pumps.
Doable? Probably. Worth it? Up to you, but I'd say it starts pretty well into the "probably not" range.
You may want to look at a jackplate or similar non-flotation (non-wetted) bracket. You won't gain flotation at the back or extend hull length, but you can probably get some deck space back. Still have a lot of the other issues mentioned above. Cheaper (most likely) as well.