We're currently switching to a system that uses the
Companion Card System as a basis*. We still have ambulant NPCs within the game, but mobs/groups/additional bodies get their own card with some bonuses.
While it does reduce the power of certain options and spells
(hiring 20 thugs for a few hundred gold/conjuring several fae creatures will always be more poweful than the card variants) we've found that it does provide a more player-centric game experience, speeds things up considerably and as a result, is leading to the DMs readily providing mobs/groups/additional bodies to support the player, when appropriate.
So, in play, when your player/players cast Summon Woodland Creatures, you grant them a card that represents the creatures supporting them. It's an abstraction, with a finite number of health levels (typically 1-4, are lost when the player is hit/crit/drops unconscious) and grants a constant buff (bonus to damage and/or defense, for example), a once per X (turn/encounter/rest/etc) bonus and perhaps another bonus depending on their loyalty or another factor. The clever thing about this system is that, because it does streamline things to such an extent, you can probably let the player choose the creatures they summon - a defensive option/offensive option/control option/utility option and so on.
And when introduced consistently, the relative 'power drop' is largely redundant. Of course, you will need to do a fair amount of work yourself, simply because the .pdf is lacking greatly in details and supporting material. Basically you're paying 5 bucks for suggestion of an idea. The rest will need to come from you.
[sblock]
*Micro review: Good idea. Overpriced. Not enough detail on creating your own cards. [/sblock]