Weights def a concern with a 200g tank plus around 300lbs of stone and 100g sump not to mention liverock etc.
I'll be making the stand out of 2x4 first to support the tank, I'll be using 3/4" plywood plus 2" s&m foam for the tank to sit on. then I'll be building walks from 2x6 on the outside of my 2x4 frame to hold my stone and create my shelf. If I build from just 2x4 with the shelf it won't support the tank as it will be wider, so my plan is to build framed walls and supports for the tank then build a stand from 2x6 in two halfs that will fit around the interior stand like two horseshoes
then just granite for the top cut to fit around my tank in two halves also