Mmmm...
Whether we like it or not, there is a British Standard for number plate.
And whether we like it or not, there are legal requirements regarding reg plates, if anyone chooses not to follow the law, then that's what they're doing, not following the law.
If they break the law, will they get caught/prosecuted? - Who knows.....? Not me, guess its a bit of a gamble, but what are the odds?? Put it like this, is the chance of getting caught greater or smaller than winning the lottery? - bearing in mind you're more likely get struck by lightening than win the lottery - but people play those odds wanting to be the one, and reg plate odds
not wanting to be the one

From memory, a Q plate identifies the vehicle as one of undetermined age/origin/ parts/whatever, and the Q plate is the first official registration date, so I'm guessing that by default its not pre '73, and therefore not eligible for the traditional pressed Ally/Steel plates
If the owner of a Q plate vehicle were able to legally transfer a pre '73 number plate (and I'm not sure if you can can do that with a Q-plate), then having a pressed Al plate would be, in Manky's case, in keeping with the vehicle's apparent age, and therefore wouldn't stick out like a sore thumb, but (if it didn't meet the reflective regs etc etc which applies as the vehicle was first registered in 2011) it would be illegal.
I've seen modern Royal Enfield & HD motorcycles with black n silver rear plates to make the bike look 'old' (trouble is when it starts AB57 … it just looks plain wrong to me), I'm guessing the legal plate is put back on at MoT time. Don't know if these machines get stopped by the authorities, but I'm guessing those that do change them, and those that don't carry on??
I don't know the answer to this, but I've seen vehicles with two sets of plates, the standard UK plate and an American plate, so may be worth finding out if you can fit a traditional 'show plate' pressed plate as well as the required reflective effort ??
Food for thought................