Are you sure about that?
In this case, I would use a powered DECA and feed the Genie with ethernet and add a BSF filter to the SWM input
Um why? I've heard its not good to put a bsf right next to a genie as it reflects the signal back to fast possibly.
If he didn't use the genie as the bridge,I'd use a 2 way splitter then use one line for the genie and one for a deca connection. He will need another power supply for a deca though if he does that. His other receives aren't going to drive an external deca anymore.
I'd put the genie not he most important spot, the h on the second most important, and the HR24 not he third most important.
Actually I'd likely swap the the h25 for a genie mini. Only can gain from that. Can't lose anything.
And keep the HR21 as a backup in a closet somewhere!