We won’t have enough Nimrod MRA4s to use them as bombers. They’ll be rare & precious things, far too valuable for their main purpose to put them in harms way dropping bombs if we can avoid it. They’re also easy targets for any kind of air defences, so only usable for launching stand-off weapons where that can be done from a safe distance (& very many targets would need getting into the danger zone even to launch Storm Shadow), or in a permissive environment.

They don’t give global reach without a network of bases, overflight permissions, & tankers, & deployments are hard to hide, unlike SSNs.

The advantage a penetrating strike aircraft offers over SSNs is the ability to launch repeated attacks, & attack multiple relatively low value targets, which SSNs with a small number of expensive TLAMs can’t do. I see this as an argument for something like a long-range stealthy UCAV carrying PGMs in addition to SSNs. I don’t see much of a role for a very high value, non-penetrating strike aircraft.