I havnt followed through with Michaels solution yet, but using mine you could create a much larger surface than needed. Then trim out your initial shape, and DONT use "ShrinkTrimmedSrf", then manipulate your points of the new shape. Then when you want more points, "Heal" the surface by drilling down to the edges and deleting them and the original large surface returns with added points!

I know, I know... Hoky. I havnt tried it with multiple "Odd" shapes yet, only one large square cut down to a smaller square, but in theory should give the ability to keep adding back more points tpo the outer edge of the surface.