Large deep muffin tins sound good, though I do have a Yorkshire pudding tin a (4" or so cavities) and wonder if sandwiching two together with marzipan, base to base might be nice? It would be a bit like a simnel cake, but with the marzipan added after baking. Personally I love marzipan and a slightly softer marzipan center would keep it moist - not to everyone's taste I know though.
I have used a 6" soufflé dish for rich fruit cake in the past, but obviously these are more expensive and I did find it less moist than a big cake.
I think the idea of cutting up a big square cake sounds best, little cakes wouldn't take the longer cooking that mellows and melds all the tastes together. Might be best to leave it in one piece and feed it for as long as possible though, then it would be easier to cut to size.