I developed a few commercial games on unity a while ago, here's why some of what's proposed is harder than you think,
- The original developper is not working on the game anymore, another company is maintaining it and has no capacity for making significant changes to it.
- You can't release your server source code because you will be using a lot of proprietary add ons that can't be released, and those are usually absolutely essential.
- Your server is going to be built against a now unsupported version of the engine, that you probably can't even install on current year operating systems
- stripping the source code of 'proprietary stuff' is significant work, there's no package management, code is copy pasted.
- Your protocol is based on third party commercial code and that other company doesn't like reverse engineering
- Changing the way the networking works to remove the lobby is significant development work, the networking framework is out of date, not maintained, and the devs are most likely not available anymore.