PoP measures in LookML

[MiaData]

We have begun using this way of doing PoP  , but are stuck on two points. 

The biggest is our custom measures. As an example, take the margin of a product. We have a custom measure doing that like this: profit / revenue

But this is a number, and the PoP way doesn't support numbers. So how can we achieve having both the current margin and the margin for last year?

Also we have filters and dates - it seems you can't use the PoP without having the date in the table, and sometimes our customers ask to have fx 
product - revenue this year - revenue last year 

and then use a filter to narrow down the period - but it seems we can't do that?