You can roll your own anything with enough time and manpower. Whether it makes sense to do so depends on your circumstances.
For the last several years, due to static load we've been fine with 2 instances per service. Now that we want autoscale (even though all the real load is really just the DB), it seems we could get ourselves onto AWS autoscale in ~1 month, though it would require some coding.
Spending 3 devops on 1 year doing something is a red-flag to me. If your changes save devs 1 hour per deploy, it'll pay off 6,000 deploys from now.
I think it's great you guys have 2.5 dedicated people operating 6 services across 12 prod instances, with that kind of ratio our team would be 15 people!
When you make a change manually, there's a chance that you forget something, have a typo, etc. Those problems disappear when those same things are automated.