I think you need to find or ask a template of the jerseys try asking some of the jersey makers in the patch and release section thread they might share it with you
I think it might be possible. You will have to find a jersey that has the same exact number placement, then use it's IFF file and rename it to the jersey you want and just import the textures. Just a guess, though.
I mean, when I open the jersey with Iff editor, it has 19 sequence. This jersey is the one with v-neck. I want to make it my home jersey, but it has no space for the 'mascot' sequence. Below is home jersey:
There is 29 sequnce for home jersey. I want to imitate it but the "v-necked" jersey has 19 only.