MANs biggest problem for rewards is the lack of flights to LGW, meaning a lot of holiday destinations are unavailable (if you have to taxi from LHR to LGW, you may as well drive straight down)

Another problem with short breaks from the regions is you end up spending all day travelling. If you do a MAN-GVA flight, by the time you're boarding the GVA segment at Heathrow, you could be in your hotel if you'd flown direct on easyjet.

MAN is relatively well served with OneWorld -- AA to JFK/ORD, "FinnAir" to HEL, "BA" to Billund, Qatar to DOH and out east, and possibly others.

Pointless from my perspective though, as none of those carriers offer a premium economy

Transiting via T5 is painless -- no need for security, you just walk straight into the terminal. The biggest issue is you arrive at the wrong side of the terminal for the south lounges.