"If you are not confident about working on this site then I see a few possible routes... there are probably more
1) give the client a refund and confess that you are uncomfortable with this job"
It's not that we're uncomfortable, it's that we want to know what the community think.
"2) explain title tags to the client and how reaching for additional keywords could result in a rankings loss for the primary term but a possible rankings gain for the secondary term, then let the decision up to him
3) attack the new keywords with new pages
4) optimize the homepage with off-page methods"
Great advice. Thanks.
"None of your replies mentions the strength of your competitors. Are they soundly beaten or are the threatening in their strength?"
Good question. They are really strong.