I know the TL-WPA281 only has one Ethernet port, and it seems all of their powerline adapters have only one port. but the TL-WPA281 has WIFI function, maybe you can connect the other devices wirelessly to the adapter.:)

I recently upgraded to BT Infinity (Hub3). My previous set-up (BT Hub2) was plugged into the phone on an extension - and used 2 powerline plugs (siupplied by BT) to send a signal from the hub to my BT Vision box in another room. I just connected to the hub by network cable for a desktop PC and usually by WiFi for my laptop (or plugged in another network cable to the Hub if I wanted the faster cable link). Last year I decided to ditch the supplied powerline connectors for faster TP-Link plugs (for the same setup) - but added in a third TP-Link with both ethernet and wireless, the TL-WPA281, in another room - and that was fine (all worked simultaneously, I haven't paired anything - just plugged them in). Since I upgraded to Hub3 (Infinity) the BT engineer insisted the Hub be plugged into the (newly adapted) primary phone socket. Instead of laying ethernet cable (I may still do, underfloor when next I lift the carpet) I plugged in a TP-Link next to the hub and put it all through the mains - and it all seems to work fine (one TP-Link by the PC, one by the BT-Vision box, and another wandering as needed to other rooms [the 281 with WiFi]) so that all seems to work. What you propose doesn't sound that different. However you may need one TP-Link (each with one ethernet connection) for each device you want to connect to your network - and it is recommended that you connect the TP-Link directly to your mains socket, not on an extension lead or adapter - that may be your main problem.