I just thought of another solution which might fix this problem without needing any special syntax characters.
If you consider that the reason we know to add parentheses around structures in the first place is the indentation of forms below the current line, then it is ambiguous whether a form with no nested forms should be wrapped in parentheses or not. If the system then does not assume the innermost forms are function calls, then it solves the problem of interpreting literals as function calls. Thus you can now do this:
if
test
exp
exp2
(very-long-exp3 5 6 7 8)
(some-random-exp4)
test2
exp5
(exp6)
(exp7)
Which cleans up many parentheses (removing all parentheses was never our goal in the first place), and doesn't result in the extra parentheses that were a problem before.
Note that the above syntax is already what is pretty much the basis for all i-exprs in the mailinglist I posted, which is the main reason I posted the mailinglist.