It appears that you cannot go from a postdoc/student B permit to a C permit directly. Surely, you can easily go from postdoc/student B to dependent (spouse B) then ask for the C permit - and you'll need to then go through the process of whatever is required for a C.
Have you actually been to the local town hall and asked them if you will be able to apply for a C permit based on your current situation ?
I cannot see the disadvantage of asking the authorities to change you over to a dependent B to your C permit holding spouse, unless you don't plan to be married for very long. Fact is, they either count your years as a student/postdoc or not....
I do not think you need to be on a C for a specific number of years before applying for citizenship - it is just that you need to go from B to C then apply for a passport. I do not know if they will take into consideration your number of years on a student visa in Switzerland.
What is your reason for wanting a C permit ?
I am fairly confident that you can go from student B to dependent B then to C permit without resetting the clock. The hurdle is that you cannot be a student in Switzerland for years and years and then get permanent residency.... but as cantonal rules differ, your best source of information really is the local town hall and cantonal office.
I don't think consulting immigration lawyers is the right way to go on this (or necessary). Best to ask your local town hall where you, and your spouse live. As your spouse has a C permit and is very able to to communicate in the local language, she should go to the local town hall and ask them how to help you to also get a C permit.
Really, that's the best i can offer - the local town hall will be the key decision maker/gatekeeper and will certainly provide you with the current rules, in detail, to help you move forward. It also helps if they know you, like you and you are integrated locally. As your wife has a C permit, she knows the process that she needed to go through....
Oh, and in answer to your second question - no the 5 years married thing would not reset if she then moves to citizenship....