Talking with with friends and awaiting release from the turanny of COVID restrictions leads to the discussion question, "Okay, say we go with 6mm Fantasy for large battles, what rules would we use?"  Everything they have is 28/25mm and 20mm - their idea of a "small scale" is 15mm with one 10mm guy.

FYSA, HOTT and and thing DBx are non-starters.  These are guys who really like Warlord (familiarity) and can be convinced to play Chainmail if I GM.  
 

What rules might entice them to play? 

I have Baccus Dwarf, Elf, and Goblin.

Warmaster? Or any favourite rules just change the ranges and movement rates.

?

Sorry to plug my own rules, but I use "Warfare's Tremendous Feats" for 6mm fantasy.  WTF consists of core rules and several supplements for various periods.  The Fantasy, and the  Ancient and Medieval supplements are unlikely to change.  The Napoleonic Wars, ACW, AWI and the Pike and Shot supplements will get further troop types and maybe rules adjustments.  [The Retro-Science Fiction Supplement is also probably stable, but I don't know where to find 6mm figures for "Barsoom".] 

Nearly all my 6mm armies have been converted to 60mm wide basing.  In theory, you need a 4 foot 6 inches (135 cm) wide by 3 foot (90 cm) table for a sized standard game with 60mm wide bases, but if you reduce the deployment depth you can get away with 30 inches (75 cm) deep.  Double sized games can be great fun, but can do with a slightly wider playing area; 5 to 6 feet wide would do nicely.

WTF and its supplements are free to download, but I have a feeling that you have to join the io group to be able to access the files.

https://groups.io/g/WTFwargamerules

Never played it myself, but I've heard good things about Warband.

You can find player comments/reviews on the web, eg here.

You could always develop your own fantasy version of the Warlords if that will get them playing.