I've always had the random idea of Vandread-esque mecha; Mostly in the case if Kayto ever got his own Ryder, it'd be a special one that is pitiful on its own, but able to merge with other Ryders like Vanguards and Dreads to form a 'super' Ryder, which is the feel I am getting from this thread.
To be honest, it would be kind of hard to have pre-existing ryders doing this without extensive redesigning. I mean the entire frame and all the subsystems would have to be remade from the ground up with the intent of allowing them to merge together seamlessly. This would also be hard due to us just losing all our financial backing from any substantial military force, along with us losing our main technological genius.
It would be interesting to be able to pair up two units a-la fire emblem, but have them merge into a new more powerful unit instead of just fighting together. Perhaps instead of giving each Ryder it's own name when combined, make the secondary Ryder give a suffix or prefix to the name of the primary Ryder.
Black Jack provides- Heroic/Awoken/Assault,
Liberty provides - Techno/Diode/Support,
Phoenix - Nitro/Swordsmaster/Interceptor,
Bianca - Cyclops/Medic/Manipulator,
Seraphim - Angel/Guardian/Sharpshooter,
Paladin - Cavalier/Alliance(patriotic)/Armored,
Havoc - Grenadier/Chaotic/Destructor