I avoided building anything custom until I had to, and I avoided adding more than a single agent until I had to.
My preferred way to use AI for coding has been to work closely with a single coding agent with the code open. That changed wth 5.6-Sol and a handful of skill files. I stopped needing to watch closely to keep it from fucking up the codebase. With the right request, that combination will get the job done 9/10 times.
That unlocked a new workflow: as soon as a change is requested, a coding agent reads it and gives me a PR. I want a complete proposed code change in front of my eyeballs by the time I open the change request myself.
So I have a custom solution in place to manage a handful of agents aligned with this workflow.
Custom solutions are so cheap and easy now... it's really hard to put up with solutions that are only mostly right for the job.