Resource Template JSON editor needs to be web based and part of Cloud Dashboard
The Resource Manager templates need some easy web app tool for editing the templates on the go. Ideally via the Cloud Dashboard.
Compare to this: https://azure.microsoft.com/en-us/documentation/articles/app-service-deploy-complex-application-predictably/
The only tool with any kind of "intellisense"/validation is based on VisualStudio - why that restriction? Nice for VS users to have some plugin or whatever for their favorite IDE, however the Resource Manager is surely useful to any Azure user on any platform, no matter whether he ever laid hands on VS or is going to.