I'm also a 36D so for what its worth this is what I do

I wear a good sports bra under my swimsuit (black bra and black swimsuit) under my wetsuit. I have some shorts with a very thin chamois which I also wear under my wetsuit. The in T1 I just slip off my wetsuit and put on my shirt (and bike shoes and helmet of course). I haven't been able to find a sports bra in my size that looks enough like a crop top than I want to strip down to it