Absolutely Chriswg
I make a madras base/sauce/gravy in a way similar to that which you describe i.e. by adding typical madras ingredients to typical base ingredients to make a madras base/sauce/gravy. I then use this to make any hot curry (madras, vindaloo, ceylon, phal, jalfrezi, patia etc, etc)
As you rightly say, BIRs require a versatile base to make a range of curries from, from mild to hot. But if you are just interested in hot curries (as many on this forum seem to be), then why not simply make the base to suit, accordingly, indeed.
I agree, it is then simply a matter of adding the meat when you're ready to eat

It works fine for me (but beware that adding fresh chillies to the base doesn't seem to work too well).
In fact, I also sometimes fry typical madras ingredients and meat (e.g. lamb or beef), add a typical base and transfer the lot to a slow cooker for several hours. I guess this amounts to a similar thing (aside from adding the meat up front).