The way I see it (and how it's worked in the past) is it would be like this:
"rule proposal:
Rule xxx: blah blah
Rule xxx: blah blah
Rule xxx: blah blah"
Then people vote for it as a whole.
I can see how 302 doesn't necessarily contradict anything, but then it seems like at this point like we can already do multiple. "Proposal" isn't very clearly defined in the rules. 303 seems to say a proposal is a rule change, since it says "where xxx is the proposal number," implying that the proposal number is the same as the rule number.
Okay, now that I've been thinking about this, I think making a new rule defining proposals might be best.
Draft Proposal:Rule 208: A proposal is one or more related rule changes. They are all voted on at once. A proposal's number is the number of the first rule change in the proposal. When a proposal is approved, all rule changes in that proposal take effect immediately. (This takes precedence over the last sentence of Rule 305.)
It's in the 200 section because it's like defining rule changes and such. The precedence thing doesn't need to be there as this rule has a lower number, but I think it's good to have to make things clear.