I thought about the failure, and then ran CUPS.PDR through PMDLL (Because I know a PDR is a kind of EXE). I do this on ArcaOS, and I get UCONV.DLL depending on UCV32.DLL. There is no UCV32 on MCP or Warp 4.
This is *not* the problem. CUPS.PDR does not link to UCONV. It links to PMMERGE which links to UCONV which in turn (on Warp 4.5 at least) links to UCV32. If UCV32 were needed but missing, PMMERGE would have failed to load and your system would have blown up during boot. This is a red hering. Chances are that the Warp 4 version of UCONV doesn't even load UCV32, so it isn't "missing".
What you may be seeing is a flaw(?) in PMDLL. If I run it against the CUPS.PDR on my current boot drive, everything is fine. If I run it against a copy of that file on another boot drive, PMDLL tells me DOSCALL1.DLL can't be found - and that's ridiculous.
To fix the real(?) problem, can't you just use PIN.EXE to manually attach the PPD to the driver?