As a phonetician, I usually avoid trying to change the way people speak. I aim to raise awareness about the sounds of speech, to enable students to hear things in detail and also to let them produce various sounds; but I don't generally tell them how they should sound.
However, recently I have been working with three exchange students from China who are preparing to sit for the IELTS exam, and they have asked me for guidance on improving their pronunciation; so in this case I have made an exception. And one of the things I note is that I am telling them to use patterns of speech that native speakers do not use. Let me give some examples.
- The biggest problem is probably with voiced fricatives, as Chinese has none, and /v/ is often pronounced as [w]. As a result, 'verb' may have [w] at the start, and 'never' may have medial [w]. The solution I have suggested is to use [f]. Now, [f] in 'verb' and 'never' is not quite right (according to native-speaker norms); but it is much better than [w], and it will enable you to be understood.
- L-vocalisation (using a vowel for /l/ at the end of a word) is also an issue. Now, this is something that many native speakers do all the time, especially those from London but also throughout the UK and Australia. However, I heard 'meal' and 'feel' spoken by these Chinese students as 'mew' and 'few' respectively, and I suspect they will be marked down when taking the IELTS exam. I had problems getting them to use a proper dark-L (maybe I am not a very good phonetician!), so I suggested making these two words bi-syllabic: [mi:jəl] and [fi:jəl]. Now, this is somewhat different from how a native speaker would say the words, but it does seem to achieve good intelligibility, which is surely the main goal.
- Finally, there is use of a glottal stop for final /t/, something which is again very common in many varieties of native speech. In one recording, the speaker said 'not yet' with a glottal stop in place of both /t/s, and it was a bit hard to understand. So, even though many native speakers would do exactly the same thing, I suggested that this speaker try to articulate all /t/s carefully.
In conclusion, in helping foreign language learners of English to achieve a high level of intelligibility, we should not be getting them to blindly mimic the patterns of native speech. There are various strategies that can be used to improve intelligibility, and that must be the main goal, regardless of what native speakers actually do.
Whether my advice helped the students with their IELTS exam or not, I do not know.