Being able to, for example, build docker images on tangled would and is a pretty important feature. Currently I build all my projects on GitHub, and use GHCR as a container registry.
Example: https://github.com/Luna-devv/transgirl
For the beginning, you could just only provide a way to add our own selfhosted CI/CD runners/servers, until tangled makes enough revenue to afford hosting them.
I'm not sure whether anything is planned yet, but it would be wonderful to see support for something like act_runner.