try this doom2-dv.gpe (output to txt is optional)
#!/bin/bash
./prboom -iwad ./id1/doom2.wad -file ./wads/dv2.wad > prboom.log.txt 2>&1
sync
cd /usr/gp2x/
exec ./gp2xmenu
with this directory structure
game\interpreters\doom\id1\DOOM2.WAD
game\interpreters\doom\Doom2-DV.gpe
game\interpreters\doom\prbmsav0.dsg
game\interpreters\doom\prboom
game\interpreters\doom\prboom.cfg
game\interpreters\doom\prboom.log.txt
game\interpreters\doom\prboom.wad
game\interpreters\doom\tranmap.dat
game\interpreters\doom\wads
game\interpreters\doom\wads\dv2.wad
I also renamed the wad from DVII-1i.wad to dv2.wad to avoid case/dash issues.
I have add-on support scripts
here, but I agree that it was a pain to get working initially. HACX, Alien Vendetta, Requiem, and a few more wads are top notch and keep me playing Doom for hours. Add DV2 and I now have a hard time keeping my maps straight.