Current stack and credits limit, as i properly remember, was talked over in Q&A and it can be easily changed.
When stack limit of plex storages would be implemented, do You really think that Devs wouldn't change a little mechanism of storages?
I think it's very not likely that if we want to transport billions of blocks then we would need thousands of storage tabs. More likely is that connected plex storages would increase stack limit of one tab. So still we would need thousands of plex blocks, but without thousands of tabs.
With stack limit of plex storages, transporting quadrillions of blocks could be done only with enormous ships, but still wouldn't require millions of tabs.
I keep talking about ridiculously big amounts of tabs, because it's the only reason for automatic loading/unloading blocks as it would mean spending hours on transferring cargo, likely with huge lag.
But so far and probably also in future, having more than 20 tabs wouldn't be needed to contain as much blocks as we would like.
With current system, if anyone needs thousands of plex storages, then he needs to neat his plex storages, not implement new blocks. Damn pure laziness.
I'd like to be able to transfer cargo to/from entity i'm docked to with other ways than either making few space walks and carrying everything in my inventory or building small ship consisting mostly from plex storages, but it could be done by GUI changes, not adding new docking blocks.
BTW so far many factory enhancers are making lag spike every 5 sec, i had over 200k enhancers and ping was jumping to a dozen or so thousands. But it's likely it was due i also had many factory inputs (1 for each block in game).
And while i had millions of each block type, while moving my factory from one station to another, i've used a ship with about 20 plex storages. And remember i was moving millions of each block type, and a recipe for each type. Thus i don't understand people who has so many plex storages, opening tab is lagging their game.