That would likely be the safest option. If you decide to do that, make sure the shifters you get are compatible with the derailleur you have. Recent derailleurs from different manufacturers (SRAM, Shimano, Campagnolo) now often use different derailleur pull ratios. Hell, sometimes derailleurs from the same manufacturer use different pull ratios for the same number of speeds (example: Shimano road and Dynasys 10-speed).

One potential issue if you're specifically looking for friction shifting: as I read the Microshift website, the newer 11-speed Microshift Shimano-compatible road bar ends don't appear to have a friction mode. Their older bar end/downtube/thumb shifter units (all appeared to use similar shift levers) did.

If not having friction shifting is a "dealbreaker", short of using a jTek or similar pull ratio converter to pull more cable I'm out of ideas. VO's website specifically says that the oversized Dia Compe 11-speed downtube shifter set they sell will not fit Dia Compe thumb shifter mounts due to the larger barrel. Presumably that also means it won't fit most bar end mounts.