Instead of trying to "acquire an accent" why not focus on clarity of speech and pronunciation? If someone is unable to understand an accent, it is more often a case of that person not being exposed to differences in pronunciation which speaks more to the listener's lack of exposure than something wrong with the speaker.
Many regional accents from the UK are difficult to understand because they use non standard grammar, sentence structure and place stress and intonation differently.
I agree with the focus of most existing language learning - vocabulary and grammar are the foundation. Intonation and pronunciation are important. An accent is just top dressing - it is relatively unimportant in the grand scheme of clear communication. The goal should be clear communication, not a north american accent.