That would probably work OK, I guess, but some languages have the same keywords, so I don't think you'll get very high accuracy. I also tried a word level n-gra

That would probably work OK, I guess, but some languages have the same keywords, so I don't think you'll get very high accuracy. I also tried a word level n-grams with linear classifiers, I couldn't get very high accuracy out of it. Also n-grams with higher values for n improve accuracy a lot if you train it with a lot of data, both for word-level models as for character level.