Side Character Pipeline help for a small team

I work at a small studio and we’re few in the rigging department.
We’re working on a modest film, and we’re soon exiting pre-production. Upon examining the storyboards, animatics, concepts, etc, it is evident there will be scenes that include visible background characters (school setting, movie theater setting, etc) that are not interacting with the main cast.

What would be an efficient pipeline for us few in the rigging department (with access to help from the modeling and texturing departments of course) to get a decent amount of character variations available in a reasonable amount of time? I was thinking create 3-4 preset side-character rigs of varying heights, and have dozens of blendshapes for each of them to morph the meshes using controls. Muscle mass, jaw shape, weight, etc.

Is this an industry-standard way of tackling side-character rigs efficiently without having any additional software or plugins, or is there a better way of doing this?

Any help would be appreciated. It’ll be my first time handling this level of responsibility in a production and I don’t want to be a bottleneck to the rest of the team.

Have you considered dedicated crowd tools, like Golaem?