A couple of thoughts here. At Mom & Dad's place, we ended up drilling two wells.
The first one behind the house. I was only 13 at the time, and built it 8 foot tall like the rest of the house. Apparently it is a major pain to remove the roof to service the well (which has been done a few times over the years). Nobody told me that it had to have a removable roof. And, it should have been a 4 foot structure or so. Just barely large enough for the tank. The well crews can remove the roof it is designed to easily unbolt.
They then decided to punch a second well in front of the house. They put the tank in the garage. And, just connected the pipes and I think the control box at the well head. Around here, the pipes exit out the top of the casing. Other parts of the country have pipes exiting out the side of the casing below ground.
Anyway, we've had a couple of different covers. For a while just a 20 gallon barrel slipped over the well head. They now have just a little 2' x 2' box built around it.
It is clean and convenient to have the pressure tank in the garage, and largely frost free.
It appears from your photo as if you are already configured with a remote tank somewhere. So, I'd just rebuild a basic 2x2 structure like you have. If you want, you can decorate it some. Build a picnic table around it? Park bench? Mini Church?
Going big would just be absolutely unnecessary unless you're moving the tank in with the well head.
