I have an idea in my head and I can't seem to find pictures of something similar done by someone else. Surely it's been done before...? Or is there something about the design that makes it tricky to do? Picture attached, except my design will be 5 tiers. Anyone have experience with a cake like this?

I googled "spiral stacked wedding cake" and found a couple more.  HTH

Yes, but none of them are like the one I propose.  I guess as long as no-one on cake central can point out any major issue with a structure like this, I'll going to go ahead and do it.

It's been done, I did one like this a while ago. There shouldn't be any structural issues with it as long as you dowel it where the tier above will be sitting.