With lacquer you can melt in new material, though your chance of getting a seamless match are pretty low unless it goes back to a painter. Powder is good stuff, and it can be patched with other materials, I use crazy glue, which is very shear, and not too noticeable. There are those who say powder doesn't seal against water as well as other finishes, but that doesn't seem to be a problem in normal custom frame use. You want a beater to leave chained to a pipe out of doors...

Ti isn't my thing, but I do think it is tough to get enough compliance out of a solid material. One extreme you have oodles of fork travel , on another you get a material with a little buzz difference. Even if the material has properties that are beneficial, there are still many other variables. I think if you want a particular ride, the only way to be sure is to test it in advance. That is the single problem with custom. Unless you get to ride an identical bike, you can't really be sure what you are getting. You should get a better frame custom, but which better frame can be tough to determine in advance.

If your roads are rough rely on your tires. Torquing up your tires so they have theoretical rolling resistance advantages, when your body is getting hammered, is inefficient in direct relation to the amount of punishment you are taking. Large amount of punishment equals large amount of energy not going to forward motion. It turns out that on rough surfaces the lost energy from smoothing out the road with tires is less than from taking the beating.