I have welded up a few mounts for radar
generators. My current
boat has a wind generator
on top of the mizzen which I welded up out of aluminum
. It is pretty simple, a piece of schedule 40 pipe welded to a piece of rectangular tube that has the bottom cut off to make it fit over the masthead with a few gussets. The hardest part was figuring out how to attach it to the masthead. That is why I ended up with the U shaped tube with horizontal bolts.
Making a radar
post is pretty easily done out of two pieces of flat plate, a pole and some appropriately sized gussets. All you need is a flat place at deck
level to bolt to.
My uncle had a really clever solution for their radar which was to build a mount that hooked to their spinnaker
pole track. This wouldn't be a great permanent solution but is great for someone who occasionally runs radar and doesn't fly a spinnaker
If you really want to mount up all the things that you have listed, it will have to be a pretty hefty arch on the stern. Unless you can build it yourself, it will be expensive.