I actually like that you have few to begin with, even on larger maps. As Taslios put it, this makes it possible to focus on a tall empire and extends colonization further into the game. I think focusing on administrators should be a strategic decision, and if you have 50 of them, the techs that award administrators become a lot less important. I think modding in an administrator-awarding building as Publius has done is a great option.
I was also thinking about making a capstone tech that does this, too--or a planetary project (like training legions). A starbase module could also be added for this. Extra administrators could also be modded into a ship mission (like the mission that finds citizens).
In other words, there are a lot of possibilities for making the pursuit of administrators akin to other resources--keeping it limited makes these optional rather than pointless, giving players more control over how they play. The key is making sure the other options are equally important to pursue, and so pursuing administrators becomes one of many viable strategies.