It would be awesome to have an option to use Ardour without it reserving your sound card in an exclusive manner.
I would be happy to suffer the consequences on latency or whatever the problems might be to have this option. Latency is very rarely an issue for me, but on the other hand when I have Ardour open I often times wish to have audio on in other programs, perhaps in my browser, at times previewing samples from my command line. Many such use cases for me, and it’s frustrating to have to quit Ardour. Jack is well overkill, and not all programs play 100% nicely with jack, or require extra setup.
I have alsa set up with dmix and dsnooper so if I have an option to use those as opposed to my HW device directly, things ought to work for me.
I recognize that I don’t know what technical difficulties there may be implementing this, but I thought I would still suggest it.