First, make sure that, in the description, you make it clear "This app WILL NOT RUN on Oreo, Pie or later versions of Android".
Then, what do you care if people download 10,000 copies the day you release it or 1 a day? They're not downloading from you, that's Google's problem. (And trust me, unless you wrote an app that makes everyone who downloads it young, completely healthy or wealthy, they have the bandwidth to handle the downloads.)
Once an app is on the store, it's on the store. I can't find the date because of a (finally) recent update, but BT Mono was released back in 1012 - or maybe earlier, and it's still downloadable and always has been since it was released. So have many, many other apps.
(If the app works with a database, or even a site, you maintain, that's another matter. Then you may have to do limiting on the site. You know "the maximum number of signups have been done for today - please try again tomorrow US Central time" sort of thing. It's easy to automate a page like that. One click in an admin panel and oops, no more signups today.)