There are no clams that would thrive under that setup. I wouldn't even try the lower light clams like squamosa. They might scrape by, but I like to remind myself I could keep a dog alive by feeding him nothing but potato chips, but it's not fair for the dog
I had a 15 gallon tank (only 12" deep) with 2 65 watt PCs....and a squamosa wasn't too happy. THe second I got MH he was a VERY happy clam.
A Maxima, even high, would be under certain doom in that setup. I've seen and known people who have tried it, and the clam slowly starves to death over 4-6 months and they find an empty shell.
Not trying to bum you out, the truth is no clams would work in that setup as it is now...when you have MH, then it will be time to talk clams
Your dream tank sounds like a good idea for clams (under MH), but you may want to reconsider trying to keep everything.....softies on one side and SPS/clams on the other can be a ticking time bomb....chemical warfare between the two is a huge issue, and many people who even put one soft coral like a leather in a SPS tank start losing their SPS corals. This is why most tanks (most of those with SPS) have minimal to no soft corals, along with territory battles and smothering corals like mushrooms, xenia, etc.