> Why wouldn't a company ... let validated customer partners of theirs push batch jobs

A company standing up this infrastructure is presumably not in the business of selling time-shares of infrastructure, they're busy doing AI B2B pet food marketing or whatever. In order to make that sale, someone has to connect their underutilized assets with interested customers, which is outside of their core competency. Who's going to do that?

There's obviously an opportunity here for another company to be a market maker, but that's hard, and is its own speciality.

There are services like vast.ai that act as marketplaces.

You don't know who owns the GPUs / if or when your job will complete and if the owner is sniffing what you are processing though

Sounds like prime intellect

Snowflake ?