Looks like guys behind xVarnish are coming close to officially release this software and i was wondering if Virtualmin could natively support it. Right now it seems they will have two pricing models, one free for personal use and corporate for hosting companies. The price is expected to be around 10$/month and based on first (beta testers) impressions it looks like some "want-to-have" piece of software. Not only this, some hosting companies are already using it in production environment and they are hyped with the results.
Maybe you guys could get in touch with xVarnish devs and see what can be done. Right now they are focused on cPanel but that doesnt stop you to find some deal with them. Instead of being last, for a change be one of the first few to have it so we are not going to repeatedly see cases like it was with Cloudlinux.
Edit: Forgot to mention their website http://xvarnish.com.