It's doable. Chozn4service has his E with a front moon roof installed. Shoot him a PM.
I lost the storage box but it was no big deal to me since I had installed the SC console for the extra space. I seldom used the overhead box anyway. My map lights were not lost, I still have them and the company did a good job making them look factory installed. As for the lateral supports or cross bars, my roof was placed in between them so there was no loss of integrity for support. I watched the work being done and had consulted with the company back in 2003 with my first Element but didn't get it done until I got the one that I have now. I'm real happy with it having had it now for 2yrs now. Now leaks, creaks, or malfunctions. Also Indianapolis Auto Spa did the install and they used a special rubber seal for for the ridged roof which had to set up overnight before I got the the car back. Dancetiludrop's install which I scheduled along with mine took a little longer since he had them install a new suede headliner and sound dampening material and this pushed me from getting my car back on the day promised. Thus, they gave me free heated front seats for the inconvenience. Nothing like butt warmers. I say if you want a sunroof, go for it. Webasto makes a great product and if you go on their site, they have a list of certified installers that have attended their training facility in order to warranty the work and carry the Webasto name.
I know Dance loves his and so do I. Probably the best $1100 I've spent on any vehicle.