Look, DOPC means dioleoyl (DO) phosphatidylcholine (PC). By definition, oleic acid has C18 and a double bond, so if your lipid is saturated and C10/C8, it cannot be DOPC. It will be caproyl-capryloyl-phosphatidylcholine, or the other way around, depending on the order of bonds to glycerol - either way, it’s quite uncommon, so not sure if it has a specific abbreviation. But ok, nomenclature aside.
Again, what you’re asking is quite non-trivial and requires a good grasp of how molecule topologies work. In your case, I’d go with Packmol, and start by creating the lipid topology/structure of the C12/C12 glycolipid through Glycan builder, and just getting a single C12/C12 phospholipid through membrane builder or whatever it takes.
Then, again, use the said Gromologist functions to remove the excess atoms from the end of the tail in both cases, and edit terminal types/charges to make sure you end up with a -CH3 end. Do the same with the structures. Run both through gmx grompp to make sure there are no errors in the topologies.
Once you have the topologies of both components, use Packmol to produce a bilayer, and combine the topologies to account for the correct numbers of lipids. Then you’ll have to proceed with the standard equilibration etc. to make sure your bilayer is stable over at least 10-50 nanoseconds.
As you see, it’s doable but definitely non-standard, so expect quite a few setbacks during the process. It’s a good learning opportunity though.