Well, the biggest problem with the Me-262 is that it not only did not have "modern materials"; it did not even have the proper 1940's materials. The Germans had a desperate shortage of nickel alloys, the same materials the US used in such profligate manner for the turbosuperchargers used in B-17, B-24, B-29, P-38, P-47. That was the reason the ME-262 engines had a typical service life of around 25 hours. They had to use steel rather than nickel alloys. They were also unable to put a turbosupercharged FW-190 into production. The V-2 rocket did not use a gas generator system but instead the turbopump was powered by H2O2, which is a much colder reaction that ordinary steel and aluminum could handle. Today aluminum spray over steel is still a popular way to build cheaper exhaust systems, but they are considered to be inferior to stainless steel pipes, and the Germans had to do that as well.