Starting with modeling for BF42 is not actually a bad idea, because the limitation on polys and details also means you will require less time for it. Models for BF2 (which looks "bad" for todays standards as well) take at least quadruple the amount of time than BF42 models.
If you want to hone your skills for future games, though, I'd suggest you learn modeling for the Unreal engine. That one is very compatible, easy to use and is very likely to remain a state-of-the-art-engine. Also, it allows for about every texture trickery there is in the books (normal, spec, bump, etc. maps). With this trickery even low-poly models easily can look fantastic. Of course you'd need to know texturing for that

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