> But then you as a consumer/user of Debian packages need to stay on top of things when they change in backwards-incompatible ways.

If you need latest packages, you have to do it anyway.

> I believe the sweet spot is Debian-like stable as the base platform to build on top of, and then commercial-support in a similar way for any dependencies you must have more recent versions on top.

That if the company can build packages properly. Also too old OS deps sometimes do throw wrench in the works.

Tho frankly "latest Debian Testing" have far smaller chance breaking something than "latest piece of software that couldn't figure out how to upstream to Debian"

The difference is between staying on stable and cherry-picking the latest for what you really do need, and being on everything latest.

The latter has a huge maintenance burden, the former is the, as I said already, sweet spot. (And let's not talk about combining stable/testing, any machine I tried that on got into an non-upgradeable mess quickly)

I am not saying it is easy, which is exactly why I think it should be a commercial service that you pay for for it to actually survive.