Hoss, i'm sorry for the long delay
I guess i get the idea you're following, but i'm not sure if we are ready for this yet. because almost all "global" actions are using core-specific urls to fetch their information. not because i like to do it like that, just because that's the only way to get this information.
Afaik the Cloud-Stuff is the only part which gets his data from /solr/zookeeper – Logging loads from /solr/collection1/admin/logging, Java Properties from /solr/collection1/admin/properties and Threads from /solr/collection1/admin/threads
so, w/o having a least one core initialized .. already the dashboard will have problems, because it actually uses /solr/collection1/admin/system :/
If we can't make progress on this soon, then it would be best to commit a simpler error check for no cores that hides all the navigation (much like hte current "you need the /admin/ handler") with a clear message that there are no cores
I would prefer this one (for now), even if i don't like to have it like this (in general). Better to clearly state what's possible and what not .. as in comparison have some "may or may not work - depending on .." state?
I'll attach an small and simple patch which also shows an warning screen but with a specific message, for no cores being loaded