To be honest your 'hack' is already pretty minimal, you turn off circles once, and then add <<interface>> to each interface - seems a reasonable payoff for your end result.
However, you could write this macro:
!unquoted procedure interface($i)
interface $i <<interface>>
Which would let you write your interface as:
Note that instead of "hide circle" which hides circles for everything you can use "hide interface circle" to only hide it for interfaces, or "hide <<interface>> circle" to only hide for your interface stereotype.