Thanks for pointing me to the JIRA issue Thomas.

About templatexe standard wiki issue: yes this is known and fixed, it will be part of XEM 2.1.2. See http://jira.xwiki.org/jira/browse/XAWM-110

Note that this wiki is not absolutely needed, you can create a empty virtual wiki (without any template) and import the xar you want for it like you would do for any XE installation. The template is just an help when you want to create a wiki which is a XE of the same version as XEM bout you could want to create something else like Workspaces instead of XE.