I can completely see Clarence Gilyard as Geordi. He would've made a credible second choice had Levar for some reason been unable to take on the role. Kevin Hall might have been interesting, though would have made for some strange looking cast photos. The rest of the cast would've needed to wear lifts
Some of the rest are bizarre. It seems clear that they were imagining Tasha as Asian at some point with both Chao and Nickson in the running. I echo the sentiment though that Chao wouldn't have worked. Nothing I've seen her in tells me she would've nailed that role, so that doesn't say much for the other contenders. Bunty Bailey is a bit of a head-scratcher as I only ever recall her from the Aha video - did she do any other acting? She's pretty enough, but would have been a risk talent wise.
Frakes was probably the best choice for Riker there. Ben Murphy would have been too bland to convince in the role as it later became. Although saying that, Riker would have likely moved in a different direction with him in the role. Gregg Marx's inclusion seems reasonably logical given he won a Daytime Emmy award in '87. They perhaps saw him as a rising star and hoped to capitalise on that. Michael O'Gorman I don't know at all.
Mark Chapman is an interesting inclusion for Data. I know he's been pretty much relegated to TV guest-role hell, but I rather like him. I think he could have pulled the role off if Spiner were unavailable, although Data I don't think would have been as naively innocent.
Jenny Agutter would have been very interesting. Although the likelyhood of an American series casting three Brits in lead roles (four if Mark Chapman were hired) would have been slim to none. If Agutter had come on board, we definitely wouldn't have seen Marina Sirtis. I'll leave it for you to judge whether that's a good thing or not
Which brings us to Captain Picard. Mitch Ryan I'm not that keen on. I have to admit if Stewart had been unavailable, I would've loved to have seen Yaphet Kotto chew the scenery up.