I feel the same about this as I do about idiom brackets. I think QuasiQuotes need more love. They are a little heavier syntactically, but are flexible enough to accomplish the same thing.
blah = [ infixQ | (+) foo bar baz quux ]
blarg = [ idiomQ | pureFunc fa fb fc ]
Perhaps the extension that we should be proposing is to make QuasiQuotes syntactically lighter.
{-# LANGUAGE QQLite #-}
blah = infixQ (+) foo bar baz quux
blarg = idiomQ pureFunc fa fb fc
Obviously some thought needs to be put into multiline/precedence/etc; I don't think all QuasiQuoters would be suitable for usage in this way, but Chris's existing ideas for his proposal seems to apply just as well to this one.
(Also a bikeshedding comment: I think the keyword "infix" is not adequately descriptive for this particular proposal. I'd prefer "vararg" or something of the sort.)