I think you have covered all what's needed.
Just get a real tempo map and real time signatures.
"I'm sure lots of people are like myself, i.e. tired of flitting between different music apps and the time this all entails."
That's why I'm still here trying to get that "all in one", I was very focused on improving RealBand but all the energy was going into Biab, so these days I have just been focusing on Biab and the PLUGIN.
Before the Mac version we had a biannual release but now it's a year at a time for features to be added frown frown and "life is what happens to you while your busy making other plans".