I went through similar thoughts before I bought my POD. I'm not sure what the current price is for a POD
dome only but for $1500 for something that you still have to modify to make work, and seal and secure it, I wouldn't bother. If I had one laying around, maybe its worth it, but to buy one I don't think so.
An observatory is too valuable to skimp. You want something that you know will stand up to a severe storm.
Honestly, I think if you are considering spending $1500 on a pond to mod into a dome, check out the price on a POD dome only from Matthew at Telescopes Astronomy.
Al.