Further models had been considered, including the MVBIII, a large development of the MVBIA, which would serve as a minelayer as well as carrying two motor torpedo boats; the MVBIV, which would be a seagoing workshop/supply/repair submarine serving the main combat units of the U-boat fleet; the MVBV, which was to have a new propulsion system designed by Walter; and finally the MVBVI, which was to have a new design of steam-driven engine.