First off, there are CTOL airplanes which can deliver replacement engines to aircraft, just not F-35 replacement engines (because of their large blade diameter). USN had previously used C-2 Greyhounds for these sorts of duties, but they have too small a fuselage, and were being decommissioned. There was talk of converting some decommissioned S-3B for COD, exchanging their fuselage for a wider one to accommodate the F135, but this was not pursued. https://archive.ph/20150209193642/http://www.defensenews.com...
Second, lots of helicopters can carry F-35 replacement engines, including the Boeing Sea Knight. https://en.wikipedia.org/wiki/Boeing_Vertol_CH-46_Sea_Knight I believe that the USN didn't want to depend on conventional helicopters because of their relatively short range.
I edited my comment to make it clear it was just F-35 engines that couldn't fit. But I think the rest stands true. There was no V-22 COD variant at the time and the main COD aircraft couldn't deliver replacement engines.
Other helicopters could deliver replacements to the carriers, as you said, but the carrier would have to be relatively close to shore.
Other side note: the V-22 isn't pressurized, so they have to stay at a relatively low altitude.
First off, there are CTOL airplanes which can deliver replacement engines to aircraft, just not F-35 replacement engines (because of their large blade diameter). USN had previously used C-2 Greyhounds for these sorts of duties, but they have too small a fuselage, and were being decommissioned. There was talk of converting some decommissioned S-3B for COD, exchanging their fuselage for a wider one to accommodate the F135, but this was not pursued. https://archive.ph/20150209193642/http://www.defensenews.com...
Second, lots of helicopters can carry F-35 replacement engines, including the Boeing Sea Knight. https://en.wikipedia.org/wiki/Boeing_Vertol_CH-46_Sea_Knight I believe that the USN didn't want to depend on conventional helicopters because of their relatively short range.