If somebody came up with a basic but reliable "ROM socket + FPU" card for Classic IIs (even if it were just an FPU socket instead of the actual chip), I'd buy one right away... assuming the cost were reasonable, of course. A board that small shouldn't cost too much to make even in small runs, thanks to the various prototyping services that have sprung up. I bet the worst part would be finding that weird-ass expansion-header connector for a reasonable price. Would a card like that even need any passives on the board, beyond maybe a decoupling cap or two?