WIll unlikely cause some problem in project environnement.
But in dev environnement, when using ONE instance of Solr with multiple cores, it is very annoying;

Typical problem that occurs :

1. Launch a global indexation on a Web application (Template Web for instance). Search is working properly.
2. Then, switch to a CMS-only application (Template Data for instance). Search is working properly.
3. Re-switch to the Web application (Template Web for instance). Launch a search. It causes an error like Error from server at http://localhost:8983/solr: undefined field site. I have to relauch a global indexation just because of the schema which was resent by CMS-only application.

It seems that schema is shared between all cores.