Islamically speaking there's no problem with it. The only people who would have a problem are salafi/wahhabi cranks e.g. Anjem Choudhary types.
If you look at the roles on the Army website there is such a wide variety of roles that would appeal to different peoples liking e.g. from a Tank Crewman to Biomedical Scientist to a Legal Officer. There are literally hundreds of different roles out there. People mistakenly think that all there is to the army is being a infantryman.
I'm also Muslim (Male) and of Pakistani origin. I've been thinking of joining the Army Reserve but have been hesitating and worried that i'd get the p*ss taken out of me once the recruiters and/or fellow soldiers lay eyes on me.