My idea is that the NCF replace blocks with a diffrent one.

Say you have a structure made out of normal armor blocks in red and you want to have it made with heavy armor blocks in green, so you select exchange menue and select block one and color one which exist and block two with color two, which will be the new one.

Then after some time all blocks gets removed and welded up with the diffrent one.

That way it is much less fustrating changing blocks/colors.