I frequently use a number of guests for a variety of goals. Some, I might reboot frequently, others I might intend to use for dedicated work and might need to occasionally. However, the shortcuts for these keys are dangerously close in the typical QWERTY layout. Luckily, there's a warning that appears if you erroneously happen to press reboot when all you wanted to do was open the guest in full-screen - unless you have disactivated the warning because it's more of an obstacle than a benefit when you need to reboot other guests multiple times.
My suggestion is this: Can Host+R only reboot when pressed twice, be allocated to a key at least two key distances from any other frequently used Host+key shortcut, or have its shortcut be defined separately? Simple solutions for those of use who have stubby fingers, and no screaming involved.