Well, the size (digitally) of a 3d model isn't really determined by the number of polygons. It's determined by how much it takes to represent those polygons. So, if SQUAD could figure out how, they could possibly lower RAM requirements for the current parts. Then, and only then, we can consider 5 meter parts. Other than that, yes. Eventually there is going to be a lot of planets, and to keep part-count low for huge ships going to GP-3 or ( crosses fingers) 4, it's a must-have. Also, I think it's a better idea to make the 3.75 meter parts have slightly better mass ratios, and then the 5 meter parts could have even bigger ( but not by much) mass ratios.