One of the reasons that owners dont have their cars remapped is they have them on lease or hp and change them when they finish.
The technical reason is that there are a few faults that come up that could be expeensive if you have to pay for them yourself, but often Mazda will pay, but you mess with engine and they will claim it is your fault and not pay out .
Thirdly you have to inform your insurance company, if you don't and need to make a claim they could turn round and say the engine is not standard and we have not been informed.
There is quite enough power from the Skyactive diesels , but then having an auto you sacrifice some of that as compared to the manual.
It is possible to achieve 55 mpg on a run and 48mpg normal running in the summer if driven sensibly. But Sensible driving & Remapping are not two words that normally don't sit together.
So you pays your money and takes your chance.