Just hire an SRE. If you want to piss off your team and incur more costs than the annual salary of one decent SRE... ask your team to do on-call rotations.
In this day and age if you're a properly capitalized startup you should have the budget for one decent SRE hire. They often times double as a technical writer and are great at preventing knowledge silos in teams / members of a small team since they have to sort of know everything to be an effective SRE.
Best process improvement I ever made for my teams.