One way which works, but only partially and a bit awkyard usage compared to the integrated DVD-Player-Software is with SMS. You can start each VOB manually, but must change the language manually in a few cases...
Another way might be with OPL and a prepared image, which starts the DVD-Player.
That isn't tested yet, but might work.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux