I am just finishing my PhD and have been sent an article by someone to review (informally). It's good, but needs work, esp as the author's first language is not English. The topic is v similar to mine and I thought I could ask about turning it into a joint-authored article - we are from different but related disciplines and I think I could add to the data and the argument. But is that really cheeky?
Also, part of me does want to get another publication under my belt with a bit less work involved, but is joint-authoring actually more work? and possibly a nightmare of hurt feelings and resentment? I have met this person, he is also a final year PhD so I'm not piggybacking on his status, but still... should I ask, or is it not worth it?
yes. if this is not a formal review via a journal, then it is ok to ask.
maybe say - 'nice article. can we talk about collaborating on this topic & making it a joint article. If I put in a chunk of time, I can contribute X and Y, and I think that would strengthen the argument. but if you want to keep this as a solo article, then fine.'
you need to give the other author the option to publish alone and to not feel that you are adding 2 paragraphs to their 3 years work and claiming authorship. So approach carefully.