Not everyone agreed on a supreme court, but whatever
I'll give my personal follow up to your questions
I agree with the posts/time requirements
Senate seats need to be staggered, absolutely. If the presidential election is every four months, this is a plan that would work (although I'd prefer elections every fortnight)
Start of first Month: Presidential election
Start of second month: Senatorial regions 1,2,3 Senators "A"
Start of third month: Senatorial regions 4,5 Senator "A"; Senatorial regions 1,2 Senator "B"
Start of fourth month: Senatorial regions 3,4,5 Senator "B".
This is an election every month, with three sentors for second and fourth, and four for the third (midterm) election, one for all but 1 region.
Trust me here, 2 months with no elections will get boring very very quickly