Although it sounds like keeping IPv4 is a reasonable choice in your situation, if you merge with another company (or otherwise connect your networks) that uses overlapping private IPs it will cause issues.
Wouldn't this be true with IPv6 as well, assuming that both companies happened to have chosen some overlapping ranges?
By comparison my company uses the entirety of the private IPv4 space. `docker compose up` often fails because there is no private IP range left that is not directed through the VPN.