While not a perfect solution, a workaround that will get the editor out of the template (and give you more screen real estate to work with as a result) is to use a non-built-in template. By default, new templates are just a copy of the built-in FogBugz 8 template, so you can still have the same template, but also gain more room for the editor.
Navigate to http://[Your FogBugz Install]/default.asp?pg=pgListTemplates and create a new template. By default, new templates start out as a copy of the FogBugz 8 built-in template. Then just set your wiki to use the new template you just created and you should be all set. This is a per-wiki setting (since it is dependent on which template is being used)