I doubt, highly, it would be in the base game, as there were too few and they were only used in a specific theatre (as far as I know), but I could see the value in modding them in for added depth/flavour, if feasible. Initial rough thoughts would be:
- A doctrine unlock isn't really appropriate, as blimps would have been crazy vulnerable to aircraft, so the UK unlocking 'ASW blimps' for a +10 sub detection bonus would be inappropriate (at least on the south coast of the UK).
- An air unit that was slow and vulnerable, but had good range and decent sub detection, would probably be the way to go. That way, it only makes sense to deploy them in theatres where the enemy is highly unlikely to have any aircraft or surface warships with AA that could make short work of them (ie, coastal US - maybe south africa if Germany developed crazy long-range subs but didn't build as many long-distance surface raiders). Would rely on AI being able to be told to only deploy them to air bases in very safe places though, might be a little tricky to achieve.
Will put it on my 'list of things to look into' for the naval mod, thanks to OP for thoughts

.