I think this is acceptable.

You can do this with not using the "STOP", but you have to add a new 
rule with the same tests for each action.



You also have to change all rules if you need to change the test and 
the filterprogram  has to evaluate the same test on a mail multiple 
times.

Isn't this what NOT using the "stop checking if this rule matches" 
option is for? If you don't select that, you can have other rules 
match the message again and do more things with it.

At the moment i is only possible to preform one action per rule 
(except of stop and keep)



You can't  save a message in two folders, or redirect it and save ist 
in a folder, or redirect to multible addresses (i know the last part 
is possible with procmail if you use , or ; to seperate the 
emailaddresses, but sieve does not allow this)



It woule be nice to define multible actions like you can define

multible tests in a rule