I have a build that is going to be a 9 speed, or maybe an 8, and index shifting is an advantage
Current disadvantage is in bar con shifters, there are few choices , new? Shimano.. at 1 pricepoint.
SRAM and Campag make some too, but for 10 cog /20 speed racing no friction option .
only 1 per brand.
but the Bar end set, having a left friction shifter allows FD cage trim after rear shifts,
so no dragging chain .. if you pay attention..
As there are OEM kits, mass produced, to build up lower price road bikes,
there are lower tier Brifters. and the Ultegra D-A, & Force/Red tier as well.
Now if you lose the 'it has to index', synched with the rear derailleur, requirement,
then you have some more choices in how to go about the shifting.
just that the target is narrower as that 9th cog has to go in the space of 8.
Note: there is also Retroshift.. those brake levers can fit a down tube shift lever on their front.
My own drop bar Derailleur Touring bikes have Bar end shifters..
friction/ratchet, some I got from discard bins because they were old,
but I have decades of further use out of those.