And to be honest, I understand the reasoning, Google Workspace is supposed to be simpler to operate in comparison to Microsoft 365, and simple means a single licencing choice.
If you're at the scale where you need to worry about mixing and matching licences, you're at the scale where you should be looking at either an enterprise contract or going through a partner, otherwise you're going to be paying list price.
It sucks for people who can handle the complexity, but also as someone who has spent far too time in Microsoft licencing conversations and contract talks, Microsoft licencing is painfully complex (some licencing is across the whole tenant, some spend is consumption based billing against Azure, some licencing is requires a minimum amount against a %age of your total M365 user base, and then don't get me started on licencing machine users or multiplexing).
Partners or resellers have no reason to exist as a part of this trivial database design concern.
It’s a category error of the highest order to assume that only “largest enterprises” want or need per-user product licensing control. If anything, it’s the smallest orgs that need to be frugal at this level of granularity.
The relatively high cost of AI subscriptions just makes this error much more obvious, impossible to ignore or pretend is “actually better somehow”.
Because, you know, everyone would rather pay $200/mo so that even their gardener and the bus driver has an “Ultra” AI subscription than spend even ten minutes in a web portal assigning that license only to the sole developer on the payroll!
With Microsoft, an org can mix and match E3, E5, or E7 licensing tiers on a per-user basis. Which makes sense, because not every employee is "the same"! This is just obvious if you stop and think about for more than a fraction of a second. As a random example, I work with an org in "transport". Their backoffice staff have a bunch of advanced cloud app licenses, their bus drivers do not, because their job isn't sitting in front of a PC all day!
Google. Just. Doesn't. Get. This.
It's all-or-nothing.
Upgrade the entire org, or nobody gets AI.