Ah nice, can you elaborate how to do it via terminal?Flashing the modem is necessary to regain data since EU uses an incompatible modem that does not work with TMO.
Regarding flashing the modem, it could be done but as TWRP is kind of buggy, I don't think this is a good idea. It only really accepts .img and .zip files anyway. So to answer your question, no.
EDIT: I take that back, you could use the terminal and just dd the modem.bin to the modem partition.
T-Mobile has a different baseband, and thus is needed. Your 2125 does not have the same issue so you don't need to. Why would you think people haven't tried to get service w/o a modem flash??Not sure about T-Mobile but when flashing EU firmware for the Global/US model there is no need to do anything but flash the firmware itself. I'm running BA and have not flashed the modem. The same applies for my 7 Pro when I ran EU firmware.
Have you actually tried to get service?
Did you use the msm tool that doesn't require an unlocked bootloader? If you used this conversion method then you absolutely need to flash modem. It says so right in the op of the TMobile msm to EU thread. Also I've updated twice after using that method and absolutely had to flash TMobile modem to a and b partitions in order to have data.