Ideally the races would sit in a window where you can attract riders from all disciplines, an MMA of cycling races for want of a better comparison. This already happens with some of the big names jumping between disciplines, so it should work fine, and I think that it needs those big names at first to draw casual viewers. Would anyone posting in this thread have been posting here without the well-known names? Without them I can't see it being anything more than a niche thing and, maybe, having those top pros will raise the level of the gravel only racers. I don't really think that'll be the case, the only discipline where I think pros might struggle are the ultra endurance races, because these are basically decided by who can go with the least sleep and rest and pros are definitely not used to that.
Production will be a huge part of it, which is going to limit routes, probably for quite a long time. The usual motos could have a huge influnce on the race, which I think probably had a big influence in the course design, and I'm not sure they're willing to drop helicopter money on a series of races people may not even watch.
Yep, they'll need the names competing for it to be successful, and that also may be the death of it if they don't get consistent turnout and it's basically whichever decent WT pro turns up wins it.
I think the biggest appeal of gravel racing you've hit on the head with the safer part. I've always described gravel riding to friends as road riding the way you wish you could ride on the roads. You can kick up hills, rail corners, weave around, spread out and chat etc. without having to worry about other vehicles. Everyone I know who races/rides it feels the same way.
And yeah, as I said to Rick above, I don't think gravel racing is anywhere near a different enough discipline for unknown riders to come out and beat the pros (and that's likely clear from everything else I've posted here). The only discipline I think that might happen in is ultra distance stuff, like the Transcontinental, and even in that I think the pros who can cope with the lack of sleep and rest will still win comfortably, they'll just likely have to learn to deal with it. I think that because everyone who gets into ultra riding/gravel riding came up through the same system the pros did, they just weren't good enough/dedicated enough to make it in the traditional racing scene and now they've found a niche they can be King/Queen of. I'm also pretty sure they all know this, which is why there's a lot of noise made when pros start to turn up. Colin Strickland is a great example of that. Ok road cyclist/TTer, king of Red Hook for a little while, then big man on gravel campus but he gets beat when the pro MTBers etc. start to turn up and take it seriously.
Don't get me wrong on that last point, there are some seriously good riders in the gravel and ultra scene, in gravel many are current mtb pros/ex pros as you noted or young pros mixing things up, and I don't think any washed up WT pro can just rock up and beat everyone. Ian Boswell was probably a better than average pro, same with Laurens Ten Dam. But neither of them were really high calibre, they were on the decline and they've pretty much walked into guaranteed poduim or there abouts finishes.