Yeah not sure how drainage would work with pavers... I'd hate to say it'd be an interesting experiment, but in a way that's what it is. Since it's roofed I agree with NatJ that any water you get in there is mostly going to be from rainfall drainage from higher up seeping/washing in, so drains to divert water from doing so might become necessary, but impossible to tell at this point if that'll be the case.
Best case scenario it drains fine between the pavers and the litter materials, and any slope above doesn't feed in too much water (or the drainage compensates for it).
Best case scenario it drains fine between the pavers and the litter materials, and any slope above doesn't feed in too much water (or the drainage compensates for it).