Doing that much repetitive diving (I'm jealous!) and you'll get colder than most will diving a more ordinary schedule. The 7mm may actually be ok, tho you may be warm for the first few days. Remember you can always flush water through to cool down.
That said, I agree a 5mm is far more common for those temps.
That's why I opted for the 5mm instead of 3mm, because of the repetitive diving. And a 7mm seems a little over the top But we will see how it goes maybe the right one will ship in time. Although my dive instructor reckons I'll be the source of envy when time goes by.
Also much of my bottom time will be spent doing coral surveys, hence allot of hovering scribbling down species names. *sigh* my buoyancy control is going to be so fantastic at the end