Hiding the tab bar to replace it with a full custom implementation, instead of modifying the stock tab bar? That might be reasonable, if APIs are sufficient to

Hiding the tab bar to replace it with a full custom implementation, instead of modifying the stock tab bar? That might be reasonable, if APIs are sufficient to fully reimplement all features of stock, with no corners cut. If it's just "done, tab bar hidden, here is a sidebar for you to play in, have fun", then it would be full-on "the emperor's new extension API".