It would be healthy that it becomes more common, in fact the privately-owned public garden model of the Valetudo project [1] is the sanest way for FOSS maintainers to look at their projects.
It really depends. If it's the occasional request and I can bang out a solution in 30 minutes, I'll help. But I'll also weigh how much maintenance burden it'll be going forward. And if I won't do it myself, I'd always give some quick pointers.
Maintenance demands (your library X doesn't work with Python Y, please maintain another version for me) I'd shrug off. Wait for me, pay me, or fix it yourself.
