This idea was brought up awhile ago, and the reason it wouldn't work is because the code for doing so is missing. Right now, it's just more or less impossible to have bots in legions. Unless of course, you are capable doing all the work yourself but even if you could it'd just be a pain in the ass.
Out of curiosity though, what do you mean by training? Flag passing and such? Bots that move in predictable straight lines aren't really good for target practice because you know where they'll go every time so in my opinion it wouldn't be very effective.
You can try to find a partner who is willing to help you with flag passing and such. You two can duel and practice pretty much anything together so long as both of you are willing.
Also, your English is pretty good compared to a lot of other people around here. You capitalized I, for example, so grats.