I'm currently in a slightly peculiar situation where I will be moving to Zurich (I'm Singaporean) in June to start on a PhD position, which I have confirmed already. The plan is for current fiancee to move with me. We will be getting married on 1st May.

I'm sure I will soon have to submit my application for residence permit through the university. However, since we are not married yet, I will not have a signed marriage certificate until 1st May. I read that the approval takes 4-6 weeks, so that would be too tight to book flight and move on short notice.

Is it possible to provisonally apply for spouse residence, and then submit the marriage certificate at a later time?

What you probably need to apply for is a fiancé permit which is for people who plan to marry soon.

If that's not possible to get then your fiancée will just have to wait in Singapore until a family reunification permit is granted for her after you're married.

Hmmm you might want to choose your words a bit more carefully when talking to the authorities and possibly your future wife as well