One of the Chief's (otherwise know as God!) was a really nice Filipino who was reaching his 20th year. He was always positive and happy but as his retirement date drew nearer he seemed even happier.
I asked him one day this and he explained that with his, to us, meager naval retired pay he would be able to give his family a lifestyle as good as that of the Governor of Manila.
Back on your point, I understand it has always been possible for a foreign national to volunteer to serve in our armed forces and if accepted and they serve honorably then citizenship was on the fast track if they wanted it. But they had to legally enter the armed forces.
Point is that today we are not permitting foreigners to enter the armed forces at all, unless they are already past the immigration queues. If they are legal there is no need for them to enlist to become citizens, its just a matter of applying after 2 years. So they aren’t really foreigners.
If we had a policy of permitting a small number of foreign applicants not already in the immigration track we could select some very high quality and very motivated people.