Why don't you just courier it on Jan 2 with same-day delivery? https://www.purolator.com/en/ship-track/shipping-services/delivery-services/same-day-services/canada-us-services.page
That is possibly one of the dumbest ideas i've ever heard. If they didn't notice all the multiple applications, you could possibly have all of them accepted initially and have 4 people miss getting into the 5000 cap because of you.
If you did do this, I would hope CIC would just cancel all the applications.
There is no 5 year rule with parents sponsorship, that is only for sponsoring a new spouse.
If you and your wife's combined income meets the LICO amounts going back to 2011, then you could apply for each others parents. You would need 2 separate applications. For your parents you are sponsor and your wife is co-sponsor. For her parents she is sponsor and you are co-sponsor.
You should also meet LICO based on family size including both sets of parents. So if you + your 2 parents + spouse + her 2 parents = 6... more if you have kids.