Already many alternatives exist such as Dehashed, LeakLookup, Intelx.io, with the exception being these are paid services, but if you already have the data you can just use these sites as a search engine.
I'm not sure if KF rules permit conversation like this, as the legality of hosting websites like search.0t.rocks is questionable, but I'll bite.
Building a collection of databases is very easy and trivial, just go to a website like breachforums, buy or earn credits, and unlock free database leaks, this is what the owner of search.0t.rocks did, and that's why their data was kind of shit, there is also a torrent out there of all the databases that were hosted on Raidforums before it got shut down, you could probably find that on Reddit
The problem is going to be processing the databases, you will probably need to write a script per database to normalize the data into a standard form, the GitHub for the search.0t.rocks code has an example of this, you will without certainty run into encoding issues and fucked up data