Sounds like a question for some master modder. (You all know who you are.)
In their absence I will offer a definite 'I think so'. Seasonal healing for units works on a per level basis and buildings can provide xp per turn. Not sure of what difficulties might be involved in pulling the two together though.
An alternative I like for the Adventurers Guild would be a (very) low chance to spawn a hero for recruitment each season (maybe 1%). Maybe that is too random but it would make it well worth getting the building (to my mind) as soon as possible in a game. Certainly not something you could count on though, or plan a game around.
Someone else had the suggestion in another thread of instead having the occasional event pop from the building where a budding adventurer spawns and gets the chance to become a hero if you wager some resources on their success in a mock-quest. A few alternatives could be given from losing the staked resources (gildar or other) to making a minor gain of some sort or getting a base level champion as a result.
I feel the latter alternatives are more fun mechanisms than getting +x% and might fit better with the FE gameworld.