Under rule 103 I believe I am allowed to cover as many topics as I want with my rule. Also note that under rule 111 this is not the final form of my rule, I am happy to hear other player's thoughts first. (I want to make sure the rule passes)
You already have sudgy saying he won't vote for a rule that tries to change multiple rules, so if you want your rule to pass, then I suggest you not go with this.
I do think, however, that Rule 203 could reasonably include time limits and voting method, so the following amended version might be able to pass:
"Rule 301: Amend Rule 203 to read 'A rule-change is adopted if and only if a majority of eligible voters approve the rule-change. Voting begins as soon as the proposal is posted in its final form, and ends when a sufficient number of votes have been tallied to determine the outcome of a vote."
I'm not certain I like the idea of secret-ballot voting at all for a Nomic, at least not from the start.
Edit: Modified to rectify numbering