There's some tweaking you can do to make the application think you're on a tablet, I'm guessing it involves spoofing the device model, but it's hardly worth the trouble.
Anyway, I slapped Cyanogenmod 12 on this thing and now all is well. It can do everything OxygenOS did and everything my old phone does. Got the Cyanogen browser back too, much happier with that. However, I was expecting this to be able to set a custom search engine, but apparently it forces you to select them from a list much like Chrome does. Unlike Chrome, it actually has DuckDuckGo as an option, which is what I was looking for in the first place, so it works out just fine.
Still, it's strange this functionality isn't there. How hard would it be to edit the file that contains these search engines and replacing the URL with a different one?