Touching up a powder coating frame is not that difficult. If you stick with a standard non metallic color like red or orange then it's easy...black is easy to touch up. The trick to making a touch up look good is taping off the area around the scratch and then carefully priming the raw area. Steel will oxidize slowly as long as your not riding in the damp or salty areas. Touching up the frame is always a wise idea.

In theory powder is stronger than paint. A powder coat is a great way to save money on your new frame.

I'd love to have a titanium frame but it is rather cost prohibitive. The cost of a custom steel can likely be the same as the titanium because most titanium frame builders do not make a titanium fork to match the bike. Today it seems a lot of steel frame builders are not expressive in a good fork bend.

I'd go with a steel frame because the artful interpretation of the lugs is more eccentric than the flat brushed look of titanium. Overized tubing and lugs would be the way to go in my opinion. Consider the builder to allow your frame to allow bigger tires.

Running a 35C tire at reduced pressure in the 55-60PSI range offers a good feeling on smooth pavement. Most people are running tiny tires on bad pavement these days. A good plush tire sure beats the heck out of a racing tire with a minimal diameter and harder casing.