I'm on the fence about the liner issue. If I stick with tradition, then there must be liners. But
there are traditional knives that have no liners because the handle is everything. The old Mercator K55 and Douk-Douk come to mind. Of course, the handles are metal, but way back when these knives were brought out, the modern composites didn't exist. But these knives developed a reputation as rugged work knives that can be counted on. I've used both the Mercator and Douk-ouk, and I will admit to once in a while abusing them in the belief that they were cheap to replace if they broke, thus making them more expendable than the copy scout knife dad gave me. The Mercator was all of .99 cents at the surplus store in Silver Spring Maryland back then.
With modern material, I think you could have a very light weight pocket knife with no liners, yet still have more than adequate strength for day to day use as a cutting tool. Certainly Case thought all this out before they came out with the plastic handle peanuts and trappers that seem weightless in the pocket. Light weight is good. One of the most well known light weight knife on the market is just zytel handle and blade. The Gerber LST made knife news in 1980 when Pete Gerber came out with it. A flat little knife that you could forget was in your pocket until you needed a sharp edge. Some of the guys I worked with that were non knife people carried those LST's, and they beat the liven' snot outa them. Never saw one break. The non traditional looks seem ugly to me, but if that same construction was put into a light weight sodbusterish knife like that Gene Wiseman ultralight, and it kept to a very traditional profile and slip joint action, I think I could like it. Maybe even like it a lot. Or the Case models with the zytel handles. They sure are traditional.
If I were going custom, with modern materials, I think I may go all the way with no liners.