I could see doing a Nation without any recruitables *or* summons. And in such a way that you could only select one Pretender. The whole entire Nation rests on the ability of that one nation-specific Pretender, so you can't screw with the balance by picking a rainbow-mage, instead of what the designer had in mind
You create a Pretender-I'd do immobile, but teleportable-who spawns off a particularly nasty SC-ready sacred unit, who then *also* spawns off a different, but still thuggable nasty sacred unit, who then spawns off a good commander, who spawns a heavy infantry trooper, who spawns an artillery unit, who spawns off...you get the idea. Some of the "spawn" could shapechange into other units, for the sake of versatility, but you'd really have to be careful to pace yourself with the Nation-especially with making sure you had enough units balancing out your army.
The strengths of the Nation would be getting your toughest units at the beginning, instead of the end game, and your exponential growth. The main weakness, besides the necessity of pacing and timing, is that, if you lose your Pretender, it's all over-and losing one of the SCs should be a major blow, atleast until the end-game.
An interesting twist would be if the Pretender, itself, could shapechange into a couple of different forms, allowing you to pick which "SC type" got made when, leading to vastly different forces, at different times in the game. If each change was permanent, you can imagine the strategic possibilities, and headaches.
There'd be no Nation-specific summonables, no recruitables, and no starting gem income. You could hire independents, but I'd make your "spawn" troops cost so much gold that you'd never have a decent income, other than Luck. You could still use generic summons, ofcourse, but without a starting gem income, it would be harder. The "spawn" themselves, with these limitations in place, could then be quite meaty, without as much fear of unbalancing the nation as a whole. And each loss-except for the very bottom rungs ofcourse, which itself might be filled with various versatile troops you might not want to casually throw away-would be an unrecoverable setback to your overall endgame position.