No, but it shouldn't be TOO hard to make. If you can find the part of the rom that loads the defaul values into the VDC and edit those. I believe there are some changes needed to the editor too? Anyway, your first stop is here sites.google.com/site/h2obsession/CBM/C128/VDCinterlace
It also provides a helper-routine to adjust the register-settings to you monitor. Start it with: SYS 10260 and use the cursor-keys, +, -, Space and Shift-Space for that. If you run this routine before running the program you can then save your-version with the new register settings.
In the german 6er issue July 1988 there was a program called Maxi-Edit which provides an 80x05 screen.
Also, the C128 80-column text editor, ZED 0.77, can be shifted into displaying 50 lines. Ah, I did many a document with ZED in 50-line mode and with the use of my Sears 20-inch t.v./monitor that had RGB input.
Writing from Las Vegas in preparation for CommVEx,
... and Z64K doesn't seems to support custom ROMS =.=
Z64K does support custom ROMS. The ROM options are available via Settings==>System Config and then select the ROM tab.
If not already done, will first need to setup a ROM Set via ROM config settings. Clicking the Config button will open it up. You can also access the ROM Config via Settings==>ROM Config. Give the Romset a name, eg JiffyDOS, and populate the appropiate fields. You don't need to populate them all. Don't forget to save. Once done the new ROMs will appear as an option in the drop down list of the System Config ROM tab settings. If they don't appear immediately after saving you might simply need to start a new session of the emulator.
In addition to custom ROMS the c128 emulation of the Z64K supports internal and external function ROMs. The settings for those are also located on the ROM tab of the System Config settings.