I'm not sure which version you're using but with recent RHQ versions, or the upcoming JON release, I don't think there is that sort of limit on the number of favorite resources.  Although, I'm not sure using favorites is the best way to do what you want.  I think whatyou may want to use is the "Platform Utilization" portlet (also in the Report view).  This will list all of your platforms and a little bit about each, like cpu/memory/swap.  If the platform is down it will report those numbers as N/A (Not Applicable).  Also, the "Alerted ot Unavailable" resources portlet will show down resources.  The Inventory Platforms view will also give you a listing of platforms with availability status.