I see your point, IMO it’s too complicated to have qualifications tests, these can be falsified and comprise a lot of work.
Storage Tier is a nice idea for datacenters but not what storj SNO is for.
The amount of SNO capable of providing with a part of the data the client requires is quite big, and the amount of idle time of drives is also quite significant, so search and serve a part is actually quite fast.
Let me try and put this in another perspective, if you put one file in one drive and you want speed, SSD is the obvious choice, but you could achieve almost the same result with a lot of mechanical drives in raid0, of course latency is always higher with HDD.
Storj is a lot of mechanical drives capable of giving you that part, having a an SSD does not make a world of difference for the data hoarding people do, documents, pictures, videos, backups, etc, most will not be reused for a long while.
If you need SSD like speeds for your project, you probably need something already in the server or very close to it, i.e. to serve a webpage with static content, machine learning, databases, etc.
Storj business model is good enough for years to come, the only issue for SNOs is the price for storage, cold storage is increasing everyday, it will eventually if not already is bigger than the active storage.
SNOs get a lot of the money off the Egrees, if an 18TB drive has almost no Egress and it’s full, it could be preferable for the SNO to exit that node and just readded again in the hopes to get fresh active data to bump up the egress, this can actively work against storj trying to repair and shift the data to other available SNO.