when I bought the boat, I wanted removable aft pods ('cos I don't have any mates
4 no M10 female bigheads were installed in the deck for each seat pod, at approx. 150mm PCD. The flowcoat applied to the deck seals the bigheads and prevents any water penetrating into the hull void. The manufacturer supplies seat pods with a fully glassed base, which I then drilled through to accept M10 fixing bolts and penny washers. Bolt length is critical, due to the 'blind' nature of the bigheads.
The system you're proposing sounds good.