Welcome Russel! Boy, you sure know how to start a discussion, don't you. <grin>
The advantage of buying a coach that is already done is that you can start enjoying it right away, but it may not be exactly what you want. The advantage of buying one and then updating it is that you can make it exactly what you want, but it will take a while.
You handy are you? If you can do at least some of the work yourself you will save money AND learn more about your coach. Since it sounds like you have some time, you might want to consider buying a coach that is somewhere close to what you think you will want, use it as is for a year or two, and then start your renovation/update. If you can't do all of the work yourself you can maybe work in stages with the factory or someone near you, so that you do your part between them doing their part.
If you can afford to keep the RV you currently have you will have the best of all possible worlds. You can go whenever you want in the current rig, you can take the Airstream out when it is ready for a trip, and you can get to know your new coach before you start making expensive mistakes.
David Lininger, kb0zke
Heartland mpg 181 (sold)
1993 Foretravel U300 (for sale)