From the research I did on G-Loc in the 1980s (when things like Combat Edge were being developed) the biggest factor was onset rate, although max g and time-at-g were related issues. That's why the solutions that were applied included faster-reacting valves. However, since the name of the game was to keep the brain oxygenated and full of blood, other measures included more lower-garment coverage, to squish more blood out of your a**e to where it does some good consciousness-wise, and positive pressure breathing. (Combat Edge, F-22 and Typhoon - which also accounts for the 60K-plus service ceilings on the F-22 and Typhoon.)
I think the German Typhoon pilots are still using the Autoflug Libelle suit. This is a major update of the WW2-and-later work on water-filled suits. The fluid (same density as blood) is contained in flexible pockets that run through the garment, which is made of a material that won't stretch. Under g, the fluid flows down and the suit compresses the body from the ankles up. It was advertised as being more comfortable and more effective (more coverage, reaction exactly proportional to g and faster than air inflation). Why it has not been more widely adopted, I don't know, but there may be disadvantages as well.