The 300 f4 will be an amazing lens and with the 1.4 converter all a wildlife photographer could dream about. I am already going to try the 40-150 2.8 on a safari and it works wonderfully with the same converter.
Apart from that, the 75 1.8 is an outstanding lens that I wish you all will have an opportunity to try!
The funny ting si that actual users of these lenses are very pleased with them.
As to faster lenses: i would heartily recommend the Metabones speed adapters, used with, e.g., Canon L-primes on MFT-bodies.
Kind regards, Wim
Gear: 5D Mk II, a gaggle of primes, a lone zoom, an accessory plague, and an Olympus OM-D 1 Mk II, Pen F and Panasonic GM5 with 14 primes, 8 zooms, and 3 Metabones EF-MFT adapters ....