As discussed on e-mail thread "Sharing SolrCloud collection configs w/overrides" (http://search-lucene.com/m/MUWXu1DIsqY1&subj=Sharing+SolrCloud+collection+configs+w+overrides), Erick brought up a neat solution using HTTP params at create-time for the Collection API.
Essentially, this request is for a functionality that allows the setting of variables (core.properties) on Collections API CREATE command.
"Maybe it's as simple as allowing more params for creation like
collection.coreName where each param of the form collection.blah=blort
gets an entry in the properties file blah=blort?..."