I've done this myself. Not Latin, but other languages.
There's a series of grammar books, "English Grammar for the Student of [insert language here]", for people who need to learn formal English grammar before they can learn other grammars.
I agree. I had a better grasp of English grammar after learning other languages, although I had more success in applying lessons learned from European languages than from Asian.
These books sound useful as each language may apply similar rules or tenses differently. French limits the use of the subjunctive tense with the word "that", while English affords the subjunctive a greater range.