How to attach single step for deck where deck rim joist is not low enough to overlap step rim board
I see no reason this need to be complicated, it can all be accomplished from the front side. 

Install your pavers properly at the proper height ( this is critical as it doing the yeoman's work here. ) And know-one wants a wonky landing. 

Construct your step on your workbench to the dimensions you need. 

Install a 2x6 between the stringers ( the sides ) on the back side so it is flush with the back of the step unit and then attach your  fascia to that 2x6 backer. 

Now you can just set your pre-built step unit on your paver, slide it into place so the  fascia is up against the deck rim joist and fasten it to the rim joist from the front. 

Your plastic fascia could be a more a robust,thicker,stronger board, this is effectively a riser that is acting as as another rim joist.  If you can not find one of sufficient width then you could run  strong boards run vertically.

You could use construction adhesive or L brackets to secure the step to the paver for added stability if needed. 

There is more then one way to skin a cat. You could also just build a traditional  stringer, (  two step ) Use simpson strongtie brackets or a board at the top between the stringers and screw through that to the rim joist.