add language packs as external plugin in GWT project

I am working on a GWT project, in my product I am required to add support for n, locales and m,user-agents, hence it compiles m * n permutations. GWT take more than 2 hrs to compile these m*n permutations.

I want to add the languages packs as an external plugin, to do so i can think of one way: 1) use a plugin which fetches strings or messages of required locale.

But i am not able to process this how it can be done.

What i want to achieve:1) compile these language packs separately which reduces m * n permutations 2) and languages packs can be added to the core product and can be used efficiently.

Any tool/tip/suggestion is appreciated. Thanks in advance