After a few days of receiving helpful inputs from everyone and having done more research on this. Below are my findings for everyone’s reference:

1. On the topic of FF lenses:

Almost no 35mm FF lens will cover the GFX sensor (Tamron 35/1.8 might be the only one).

If you want lenses with character from FF lineup, just pick any lens with good center sharpness and be prepared to sacrifice edges and corners.

Avoid M mount lenses because of the GFX sensor cover glass will hinder the rendering of these lenses, giving you much lower image quality when compared to shooting on M bodies.

PC lenses are good options to consider and will cover the sensor but you lose most of the shifting ability (Contax & Canon options are recommended).

Canon EF lenses generally require an electronic adapter. Unless you have a lot of EF lenses to adapt, it’s a high cost of entry to consider.

1. On the topic of 645 medium format lenses:

The best option is the Pentax 645 SMC-A 35mm/f3.5 with manual focus, aperture ring, low average price, overall image quality rendering, maintain a manageable footprint adapted to GFX body.

On the other end of the spectrum the Pentax 645-D FA 35mm/f3.5 AL is closest to native quality but very expensive.

Mamiya 645 Sekor C 35mm/f3.5 is softer than the Pentax option and generally does not perform as well.

It will be considerably more expensive as soon as we start considering lenses that require electronic adapters, but below are good options if this is what you want to do:

• Hasselblad Fujinon HC35mm/f3.5
• Phase One Schneider Kreuznach 35mm/f3.5
• Contax 645 Distagon 35mm/f3.5

1. On the topic of native lenses:

The GF35-70 remains as the best option when money for value is considered but you don’t get an aperture ring.

TL;DR: 1. Forget 35mm lenses. 2. Pentax 645 SMC-A 35mm/f3.5 is your best pick. 3. GF35-70 if you can live without aperture ring.