Rackmount KVM Switch with HDMI/miniDP

Do a search for KVM USB HDMI on ebay. Unless you're buying cheap Chinese equipment which is still $hundreds, they are way overpriced. A software solution, such as a LaunchAgent that runs an AppleScript to enable remote access at startup on every installation would be the first option I'd explore. Having all your machines set to boot from an external USB HD that has all your remote access settings and recovery utilities in place means that they'll boot from it when it's plugged in but default to their internal HD when it's not. If it has to be done in hardware then a regular KVM with USB ports paired with a separate HDMI switching box would be the only reasonable solution, otherwise you're looking at $thousands.

Rackmount KVM for MacMini

The problems with almost all HDMI or MiniDP KVM switches in the current market are:
1. 2-port or 4-port version only, no Rackmount for more than 8-port or 12-port
2. No MiniDP KVM switches (even the 2/4-port) version have built-in EDID-emulator on each video port connected to the PC/Mac system.
These poor built KVM switches without EDID-Emulation feeding is the major problems of unstable KVM switching sometimes caused systems suspended.

A good DVI DDM based KVM switch can solve all the problems listed.
I tested ConnectPRO UD-18+ (8-port) and UD-112+ (12-port) DVI DDM+ rack mount KVM switches with all version of MacMini, MacMini Server, MacBook Pro and MacBook Air with any problems in connecting DVI-HDMI and DVI-MiniDisplayPort cables amount them.

ConnectPRO's UD-18+ and UD-112+ all shipped with standard 19-in rack mounting kit with them for no extra charge. It is the best solution for your application.