i can't understand why everyone tries to reinvent the wheel…
a sump is to hold equipment, a fuge is to hold cheato (algae). the two should not be one no more then a DSB should be "in your sump" or in your refuge.
your refuge should be stand alone from the system as should a DSB if you wanted one.
that is not to say it cannot be in the same vessel, just that they should be isolated from one an other should you need to take one off line to maintain it…
that would be like putting a GAC or other such reactor inline from your return…it does not make sense to shut down the whole system to clean refill maintain a single piece of equipment (unless said equipment is your return pump, and even then a back up or redundant pump should be used)
will your design work…yes. will it be the most effective and efficient one out there, not likely for above reasons.
use a manifold and feed your fuge separate, like you would any other filter or reactor.