can I tell the gradle application plugin to use my feature variant instead of the main, since that's where I've put my

mainClass

The plugin per-se no as far as I know. A quick look at the plugin source shows, that the main source set is hard-coded. You would need to reconfigure the tasks it configured. Or you instead add a sibling project or subproject instead of a separate feature variant.

yeah... I did, make a feature request... or was planning to. I know I made one for the spring boot plugin...