trisuit with long or shortsleeves.

^ Just fwiw, there's no way you could swim in a body paint...or any (correctly) fitting cycling skinsuit for that matter.

otherwise, +1 with the above.

I think a compression top (or tight-fitting swim shirt) would be the best bet. I've swum in them (for sun protection) and it's certainly doable; they can go under a wetsuit if needed. Not sure what the bottom would look like or what your requirements are. Maybe cycling tights with some kind of run skirt that you could pull on in transition?? There are certainly hijab-type swimsuits out there; I often compete in Singapore races and I've seen a few Malaysian women do tris in hijab, but I have a feeling they are either buying products available locally or getting their tri kit custom made, maybe as part of a club order. I remember one woman telling me she only did sprints, because the outfit she did have was too hot--she and her husband were trying to figure out how to get some of the newer cooling tech fabrics (such as 2XU's Ice-X or Pearl Izumi Innr Cool) made into a suitable outfit for her. May or may not be an issue with you depending on climate.

As far as I know, you can have arm coolers on for the swim. (Though you should check with the rules and race organizers.) They certainly wouldn't be a performance aid. Might have difficulties getting a wetsuit off, though, as they can get bunched up, esp. when putting on/removing the suit. Another thought--look into some of the products made for sun-sensitive people--you might find something that meets your needs. Or contact Yanti (Tri Aya) on this forum--she's from Indonesia, runs a tri club, and might have some ideas.