I always prefered that leaders not be lendable. Nothing worse than finding the games best generals defending rinkydink minors half way across the world. Second, while normally a nusiance only, there are times when a lent leader has a major impact on the game, like dropping Wellington on the Swedish Corps. A large (more than one corp) army with normal morale levels and a 5/5 leader? Russia better come strong, and will still have an equal chance of losing many battles. That means Russia has to swarm this nation with 40+ factors for a good chance to eliminate the force before it gets eco phases in for additional infantry...point is, this impacts the entire political balance of the game...for a minor (yes, sweden is the best of the minors, but still and minor).
Not to mention leader deaths. Can't you just see Nappy dieing to defend Naples, and not bringing French Troops? You want a leader on a minor corp, declare war. Then the minors corps are your corps, and you can do anything you want with it, including putting a leader on it.
This game aint for the faint hearted, lol.
...nothing is more chaotic than a battle won...