The P-38H is the plane that Combat Tour needs for the early USAAF/USAAC part of the tour. It is the plane both the 20th and 55th FG's went operational in. It would probably make the logical 4th P-38 model, if you figure that many of the popular planes have 4 or so models available.
It does have a performance advantage over the P-38G. I figure that HTC won't do it though, as the P-38J began trickling into the 20th and 55th FG's about two months after they went operational, and they probably figure the P-38G is close enough for the first two months of the tour. If you perform well on the first two months of the tour, you'll probably get a P-38J early in the tour. I'd like to see the P-38H added, but I'm not betting we'll get it, the P-38 has been reworked recently, so even though it wouldn't be a massive rework, they'll probably skip it.