Assuming that you actually "need" these subnets and can't do as @MichaleHampton suggests in his excellent answer...
If you don't like idea of hiring 50 AD admins, you hit your network administrators with the nearest hard, blunt object until they stop making such fundamentally awful design decisions.
Really, I can think of no earthly justification for thousands of ["real"] subnets*See "footnote", beyond the curiosity of seeing how big a mess you can make of something in a lab or test environment, and anyone who even does approach that number of ["real"] subnets is a massive multi-national corporation with a market cap larger than most country's GDPs, or is a large national/trans-national ISP/hosted-service-provider. And in both cases, they literally do have dozens of people on staff to keep it somewhat sorted.
There's just no way you're going to be able to get a handle on this otherwise. Either hire dozens of people to sort it out, or change the network design to... suck less... and be even remotely manageable by less than a platoon of sysadmins.
Honestly, don't even try. It's got "fail" and "burnout" and "awful idea" written all over it. Trying is like rearranging the deck chairs on the Titanic after it hit the iceberg. Any improvements you are able to achieve are soon to be overshadowed and undone by sinking down through several thousand feet of icy water, so your time is probably better spent reclining on the deck chairs, grabbing some liquor and a smoke, and enjoying those last moments before you're swallowed up by certain death. (And I can't tell if I'm being metaphorical there or not, FWIW, I know 3 guys in IT who've have heart attacks before 35 from this kind of insanity.)
And, of course, if you can't change minds of your superiors or network team, well, you can't marry a corporation in any country I'm aware of, so your best option might be to leave. No job is worth having a heart attack in your early 30's over.
By "real" subnets, I mean to say subnets that are actually used as such. I've been in hosted service environments with thousands of customers, where each customer gets a simple, flat subnet that's not actually managed or changed by the hosted service provider, but it definitely does not sound like that's your use-case. If it is, let me know and I can adjust my answer, because that's fairly easily handled with an *AMP database (or *AMP-like product).