It might be worth measuring some commercial stands to give you a starting point. If you live in an earthquake zone, add a safety factor to account for that. Tall, top-heavy machines like floor drill presses may benefit from an anchor line fixed to an overhead joist.

Also, consider work envelope when arranging machines. For example, a window or hinged flap in line with the left end of a lathe spindle can allow you to accommodate longer workpieces if those are in your future.

Shop layout is a complex task. I contend that it must be evolutionary. One doesn't know what's best for himself until he actually works in the shop. Plan for easy rearrangement; your chance for being happy with the initial layout is very minute.