Hello Henrique,
I've been running exports of source systems in SWPM with the sidadm user without any problem. It was my understanding that it was the system installation, or import of the new target system, where a non-sidadm user should be used. What are the perceived issues in running the export as sidadm?
Likewise, the user doesn't have to be a domain admin if the domain users and groups for the target system already exist -- in this case it just needs to be a local administrator on the target host. As domain admin is a carefully controlled access, many customers have to get the users and groups created ahead of time, before proceeding with the installation.
You're right on about the JAVA_HOME and JRE bits. That has caught me out before, where an old 1.4.2 JRE still existed on the source system, dating back from the original installation years ago. However, in that case, I couldn't even get SWPM to run until I removed the old JRE.
Regards,
Matt