Well, I suppose I can imagine a 'Request Merger' button that sends a request to the fleet you'll be merging into, but there are problems.
Not everyone is going to be at the same level. The obvious answer would be to update the final fleet with the highest values of the two. Say fleet A is further along in Tactical than Fleet B, and Fleet B is ahead in engineering and science, you get the Tac XP from fleet A, and the Sci and Eng XP of fleet B. Same with interior projects. Ones and zeroes, copy the ones.
There can be no projects in progress in at least one of the fleets. Alternatively, the fleet sending the request has its in-progress projects discarded, as these will be almost always completely impossible to merge into whatever the other fleet has going on.
Or rather, permissions. Your fleet might have fairly small differences between ranks 2 through 5, while the other fleet might attribute massive advantages and responsibilities to the higher ones. If you merge your two fleets, and Fleet B, with a few rank 5 members, suddenly gets a dozen or more new rank 5 members who were never trusted with any privileges in the first place, disaster will almost certainly ensue.
Therefor, all members of the fleet requesting the merger will need to be introduced into the new fleet at rank 1. This may include said fleet's leader. We've had more than a few incidents in this game where the top rank in a fleet was held by more than one person, and one of those backstabbed the rest, through demotion or dismissal. If this isn't dealt with preemptively, you're not going to find that many people jumping at the chance to merge their fleets.
Obviously, which fleetbank is bigger is the one that stays. But then, it only costs something like ten million credits to upgrade a fleet bank to its maximum size, and almost any fleet in existence has done so. The problem comes from the content of the fleet bank. You can't merge two full fleet banks into one.
So one of the fleet banks has to be emptied of everything, except perhaps credits, before the attempt is made. Or the contents will need to be discarded (either poof, gone, or auto-vendored at 40% and added to the credit pool) in the process.
Five hundred members is it. This is not much of a problem, since you're asking for mergers for smaller fleets. I doubt though the process should only be available to fleets below a certain member count, so that's another check that needs to be made. Though the large fleets have been asking for larger fleets. If you could accidentally merge two fleets to make a fleet with more than five hundred members, say six hundred, and the cap remains in place, you would not be able to have anyone new join it unless one hundred and one people packed up and left.
So the short version is, this might be possible, but it'd be a hell of a lot of work, and Cryptic's position will probably be: How hard is it, really, to take the handful of members of a small fleet and join another one (the generally better developed of the two) manually? You're asking for a fairly small benefit at the cost of an awful lot of work and the potential for exciting, new, gamebreaking bugs.
And this is just the quick way to do it. If you want to be able to negotiate your rank in the other fleet ahead of time, or set other conditions for the process, it's going to be that much more complicated, time consuming and prone to bugs.
yes this would be cool, but lets be honest, it is just not happening...because of technical issues listed above already.
as i see it a t2 base, even if it seemed much work, in reality is not really that much compared to t3, t4, t5. and if you consider that it is only a quarter of the actual fleet progression, this becomes very clear.
merging 2 lvl 6 fleet is still early enough...even t8 is early enough. after that it is easier to just recruit new people.
so if you desire to merge 2 t2 fleets, just pick the one slightly more advanced.
also many fleets where already smart enough to merge before season 6 went live, if you havent figured out that building fleetbases is a massive resource sink before hitting fleetlevel 11, it is not cryptics job to fix that.