Best logic for these membership options

I'm asking this question on forum as others might have same questions. Or you might have already solved this question.

For our club, there is only one type of membership. BUT ... members can pay for 1 yr or for 3 yr terms. Also, all subs expire on same date ... 31 Aug, regardless of the year. Also, we are using the prorated payment option.

In Membership Pro, I successfully set up two plans ... one for annual membership fee and one for 3 yr fee. BUT ... then I realized that I need to treat these two as the SAME plan. If a member pays for annual membership, I don't want them to see the 3 yr membership as another option. Also, regardless of which length of membership they have, when they decide to renew, I want them to have choice of 1 yr OR 3 yr plan when they renew.

MY CURRENT SOLUTION: I disabled the annual membership plan and only allow initial membership for 3 yr term. (Dues are very low so that will be OK with most). Then, for renewal options, I have set two options: 1 yr and 3 yr.

Even so, I think some will ask for one year membership term. Also, occasionally, we offer annual memberships for free (for various reasons) and I am not sure how to create a backend annual membership that is for ONE year but that Membership Pro sees as the same as the 3 yr membership plan.

Any suggestions on a better way to set this up? We have not gone live yet.

Can I create ONE plan, with two options (3yr or 1 yr term) that still uses rule to have subs expire on same calendar date, and prorated? (I don't think so) If not, does it seem I have used the right logic as described above?

My settings are in screen shot.