Great idea!
Having even one German U-boot type tuned to be as realistic as possible along with realistic and fully functional German campaign on Pacific and Indian Ocean would be great improvement of SH4 and I think maybe a good modder community answer to sad UBI's SH5 story.
GWX4 has gone and stock SH5 is a ridiculous bunch of bugs so we have to think about some SH3+GWX3 replacement basing on SH4 engine...Sorry, but SH3 graphic engine is now too old, SH5 is quite a bit resources consuming game. Yet SH4 looks still good and has some potential.