I’ll just chip in that I’d happily buy Cubasis today (my iPad Pro is currently more powerful than my laptop!), but I haven’t bought it purely because I discovered it lacks this. If I can’t change tempo or time sig in a song, it’s massively limiting to most of the songs I’d likely write and just makes what appears a great app completley useless for a lot of my songs. No offense to some people’s music, but everything being the exact same uniform tempo and time sig all the way through is one of the things that’s wrong with modern “popular” music IMHO and makes it all sound boring. It’s a basic for “natural” non-computer written music.
Anyway, lack of this feature is a straight up no-purchase unfortunately from me. Sorry.