kinoko wrote:that's not really necessary. there are only a few exceptions to the rules for telling if a verb's class one or two, and i don't know of any exceptions to the i vs na adjective rules.
There are a number of i/na exceptions, the most common being "kirai" (嫌い, "disliked"), a -na adjective that ends with -i. Things that end with -i can also be nouns, like "hitokui" (人食い, "cannibalism"), and if you want to get technical, 嫌い is one as well (the stem of the verb "kirau" (嫌う, "to dislike".)) Lots of potential for confusion here if the parts of speech aren't listed.
There are also lots of cases where verb group 1/group 2 is ambiguous. I don't know how many, but I'd guess hundreds. And not just with higher-level verbs: even "hashiru" (走る, "to run") and "iru" (要る, "to need") are exceptions to the general rule.
Giving the part of speech is standard in dictionaries, and it's actually built into the dataset that they are using. It would be very easy to implement.