Stephen, at the end of the day it is your call, and if you want to try the pier thing than go for it, just don't want you to go to all this work and find out that it really doesn't make any difference to your imaging.
Many here do some fine imaging with tripod alone, and with a little fine tuning and practice you can easily be one of them.
When I was imaging i did have a pier, and it served me well, but my situation as with others here are all different.
There is no reason why you cant have a small observatory and have your stuff on a tripod inside it.
If you try this nothing is lost if you find it unsatisfactory, and you can still construct your pier later, however if you do the pier first and find it unsatisfactory it would be harder to go back to the tripod as the pier would be in the way.
Like I said it is your call, do what you feel is right for you.
Leon
