This loco has a few things going for it - it is pretty darn big, even for a Euro loco - MUCH bigger especially in height, than the same scale British 9F. Unlike the 9F, the Class 44 is a three-cylinder loco with a big sticky-out third cylinder tail rod overhanging the buffer beam/pilot, although the third cylinder is a dummy.
It has an eight-wheeled tender, so you would also have to build a six-wheel BR-type tender - 'Mr Aster' does not sell tenders for the 9F as individual items.
The steamy bits are made by Regner, just like the S3/6 (I have a green S3/6, and so does Rod Blakeman), and it should, like the S3/6, be a mad hauler.
Aster made one a few years back, THEY haul mountains.
As for faking a 9F out of one, you might fool a model train fan from Botswana or Mars, but you wouldn't fool anybody else...
It looks FAR too German to me to be anything else. The French had a few in green without the smoke deflectors....but that just looks, well, like a German locomotive painted shiney green - the railroad equivalent of a British racing green Ferrari.