Grukhas, like Jedi Knights, can merely protect but they can't fight an outright war.For cases like fighting for Singapore, we've had FT around for that as well - the Gurkha Contingent.
For any given job you have to hire the right people......
Even if war comes, Grukhas still can't fight a war for us. We'll still need stormtroopers... erm... our own Army.
There ain't enuff Grukhas to even form a full Battalion, much less an Armed Force.