I don't think your friend should try to "work round" anything, as it could lead to much bigger problems later, by sending the wrong message to INZ about their relationship. Also, they should bear in mind that any lie in any application to INZ can be interpreted as fraud, which can cause visas to be annulled, and block any future applications.
If the wife switches to a different visa, NOT a partner-sponsored one, and the husband applies for residence without her being included, it looks as though they are no longer partners. Then later, if she tries to apply for residence sponsored by her husband, INZ can say, for instance, 'But she wasn't included on your residence application, which breaks the rules if you were living together, and/or now we don't think you have a continuing relationship.'
I found this
https://www.immihelp.com/nri/indianp...-of-birth.html, which your friend could check out, as it suggests a different method of getting the DOB changed (rather than going through the court) - notice, he should check this out with the Indian authorities.