Well there are def. more possibilities.
You can ally in elves, Gondor, Arnor and use warriors of lake town or dale to proxy men of rhovanion.
The shire folk seldom fought, but according to shire history they aided with a company of archers the forces at the battle of Fornost.
see
http://lotr.wikia.com/wiki/Battle_of_Fornost for more info.
Hobbits did not only live in the shire but there are more places where they lived like in bree for example. You could form a bree militia with men and hobbits for example..