If it helps anybody (using Magento 2.1.4), I managed to do this by first adding my CSS file to the exclude list in my view.xml
I then created a new cms_index_index.xml and put it in
Then added this to remove the file from the homepage...
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
I thought this would mean that the file is then not minified and merged for all other pages, but no... it still appears in my merged and minified master CSS file for all other pages (except the homepage)