One intriguing idea I had recently. 5G M.2 cards are large, but thin (like 2.5mm). So, if one did an expansion card which had an M.2 slot oriented inwards (toward laptop center) so that the card was ever so slightly under the laptop body underside, covered by a thin shell, it could fit into the space created by the rubber legs when the laptop is sitting on a table. Basically the expansion card would protrude inward and under rather than outward… (could protrude bit outward for antennas)