Pj,
I know I am the new kid on the block, and I hope no one minds my speaking up here. The following is of course just my opinion/suggestion.
It sounds like we really do need to move to non-deprecated forum format ASAP - the latest issue with registration failing due to captcha is an example of why.
Did I understand correctly that you could move the content, but that the trouble is with the customizations?
If so, why not move soon, and then over time build the customizations as projects in the Technical Guild? If the projects are small enough, I bet people would take them on.
While I do not know pHp and Drupal, but I used to be an ASP programmer in the days before ASP.NET. I work now mostly as a SQL analyst with strong SQL skills. I am also as mentioned in a PM to you strong in quality control and troubleshooting, I did that for a great number of jobs. Even if I do not know pHp yet, if the assignment were well defined, I am great at searching for code pieces in libraries on the Web and modifying them based on bits and pieces I learn here and there. I could not commit a lot of time, but if what was needed was occasional support for small project pieces, I could pitch in, and I bet others could as well.
I think moving the main functionality over first would be a good idea, and then if people miss the customizations they would be motivated to help make them happen one step at a time. I think if you wait until we have a developer who has the skills and time to do all customizations, we run the risk of the forum becoming non-functional before a new one is ready, or anyway the timing may be rushed then and the hand forced to move in the last moment. Whereas if we move before customizations can be achieved, then there will be time to make them happen over time in baby steps.
Software development nowadays is moving more toward agile development which consists of developing small parts of the project in two week chunks rather than trying to have a plan for the whole project all at once. So if there is a way to break up the tasks into little units, I think that would be more achievable, and if we cannot find skilled and available programmers, several of us could learn I bet as long as we had little tasks.