Now that I'm about halfway through renovating my first Scamp 19 and becoming familiar with it there are several mods I would definitely do if this were going to be my daily camper.

1. Mod 1 I would be motorizing the landing gear. Cost seems to be around $150, fairly simple to do and that is a lot of cranking with the manual system.  
2. Mod 2 I'd buy some 4" foam insulation sheets and cut it to fit the sections under the loft and cement in place, then fill any seams with expanding foam and paint black to match the landing gear. That would really improve the comfort level year round in the lot bed area. Inexpensive and simple mod to tackle with a big upside.
3. Mod3 I'd get the 8" Queen spa sensations mattress at Walmart and put the loft cushions on it to draw the pattern, then cut it with the electric knife and fit it in the loft. You'd then have a one piece custom marshmallow to sleep on.
4. Mod 4 I'd convert the dinette to a U-Dinette with a smaller table on an RV pole setup so it's easily removable. You'd then have a nice lounge, dinette, easy single bed or full bed capability.
5. Mod 5 I'd remove the 18x25 vent in the loft and modify it to take a nice maxxfan.

So far these are the very first changes I would make for the long term on a Scamp 19 for me. I'm sure I may have more thoughts as I complete it.