In theory, you could use many other verbs, but you won't hear natives do this very often. In colloquial English there are a few usages which are more common. Also, most native English speakers use the conditional tense with this type of phrase. For example:
Don't you think it would be better if we finished cleaning the house first?
'I couldn't agree more!'
Are you enjoying your new life in Australia?
'It's incredible, I couldn't be happier!