Why can't you do that now? Are you assuming WotC 5.5 only with no wiggle room? Because throwing self-imposed limits on what rules you're willing to use just makes getting what you want harder.
It suggests it might be a problem for your group, but allows you to make your own decisions and doesn't use the rules to force you to play a certain way. At least, it didn't when originally published (I know they made changes to their material when they "updated" it to 5.5 and put it on DDB, So...
It is a tough one. I think it's important to remember that everyone at the table should be enjoying the game. That's the GM and all the players. If someone (or multiple someones) aren't having a fun experience, it should be addressed to see if anything can be done. Otherwise it's simply time...
The Mage Hand Press Necromancer can have about as many active minions as the Diablo necromancer, particularly if you let its class feature minions stack with the spell-animated kind (which the class has as a sidebar option).