The SA-35 doesn't look like a C&S Hi Power. It doesn't look like a Garthwaite Hi Power. It looks like a Hi Power with an ill conceived ring hammer and better sights. It's a pretty gun, but it doesn't have any of the working over that custom Hi Powers have. This is basically a gun you would buy to send to somebody to make into a nice Hi Power.
There are a few awful details about the Hi Power. One is hammer bite, which Springfield didn't do much to correct. One is the awful trigger geometry, which they also didn't correct. One is the shitty recoil guide rod, ditto. One is the mag disconnect, which they did fix. One is the sights, which they didn't do very well with. Finally, the lack of texture, which they also didn't correct. People have fixed all of these on hi powers for years, other than the guide rod, which should be trashed. Overall, it is like one of their low grade 1911s. Nothing to get excited about.
Now, the new FN one might suck balls, and the proprietary issues are something, but it won't suck balls because it failed to address any of the issues of the original Hi Power. It will suck balls for its own reasons.
Also, the thumbs forward grip was literally developed on 1911s, which are an older gun than the Hi Power. Anybody shooting otherwise is just weird these days.