I love this idea. A couple of ideas from the ADV / sport touring camp...take them for what they're worth, if you're aiming at that market (and you should be).
Someone mentioned in an earlier thread that Jesse bags are the standard - they absolutely are, though there are other good hard bags out there. I had a set of Jesse's on my '13 GS, and I just ordered a set to replace them (the bike was totaled).
Cost is clearly not our primary concern; it's value and customer service. With the Jesses they cost an arm and a leg, but they're well made, battle proven and the internet is full of stories of above and beyond customer service where the customer is in the middle of nowhere. Don't expect to just sell a product and never have to pick up the phone and chat with a dude who has a bent latch in Columbia. It'll happen, and that story will be a part of his ride report... People should be looking at your bags thinking "they're less expensive than Jesses and I won't look like every other adv wannabe" not "those are just a little bit more expensive than ammo cans, I'll just try this myself".
The Jesse bags crash well. I put mine through hell before I was hit head on at 100 kph. While a lot of ADV guys just ride to starbucks and pose, some actually go places and do things and sometimes the bikes just want to take a nap. The mounting system is a key part of how the bags will stand up over time, and some mounting systems are better than others. It's unhelpful to have a hard bag survive only to have the mount break, or even worse to have the impact force transmitted straight to the subframe of the bike and then have that snap.
The failure modes of the bags / racks needs to be considered as well. If something goes wrong, can it be repaired in the field? Can a dent be banged back into shape? Is the hardware all easily available, or is it some specialty nonsense I can only order from you?
The bags absolutely, without question, have to be waterproof. That's the lowest expectation. Will you sell a removeable liner or pannier bag?
Some others talked about the placement of the hinge, and gave some very good reasons why the hinge should be at the front, if there's only one. One feature of the Jesses is that they open sideways, which is a non-catastrophic failure mode.
Are locks available for the bags?
I'll echo the others' thoughts that you did a great job, and if you're serious about this there's room in the market. You just need to pick the segment you're going to start with and get it right. The adv market is full (I wouldn't say saturated) but it's mature, and therefore ripe for a newcomer to steal a sliver (of a HUGE market) of business away from the big guys. One thing to keep in mind about the GS / adv market is that almost without exception, every bike sold is going to have a set of bags on it...
Good luck!
(and make sure that stickers can go on the bags easily. They add horsepower.)