Yes, it's perfectly fine to have the H100i fans as exhaust (I did something similar myself a few months back after some testing during rejigging of the rig it was in).
If you only have 1 AIO unit that cools only 1 item (CPU or GPU), then it is better to have that AIO unit in an Exhaust configuration and draw the rest of the warm air out of the case through the AIO rad instead. Like what the others have said however, this only applies if your AIO is able to handle the temperatures that are being generated from the item you are cooling (CPU or GPU), and if it is in a suitable location to do so.
Looking at the case you have designated, it looks like there's three mounting points for AIO's, and the top still looks like the best option to place the H100i with its fans in an Exhaust (blowing air out of the case) orientation. This is because the bottom and side placement for the AIO appear to be less optimal if you have them blowing external cooler air into the case through the H100i, which will create more warm air inside the main section.
The bottom location in Exhaust will try and blow warm air out, and I think everyone can see where that's going to go wrong (since warm air will generally rise back again anyway). And if placed into Intake (bringing in external cooler air into the case), the H100i will warm up that air enough that it will then blow this air into the main section and onto some hot GPU or other discrete cards as well. So this location is undesirable and not recommended.
As for the side location for the H100i I would say is a grey area. In theory, having the fans at the bottom or top as Intake (blowing external cooler air into the case) and then having the H100i pull that warmer air through to the side section on the other side, should make it cooler, but possibly may have some heat buildup if the small section on the other side of the case can't release that trapped warm air quickly enough, which may be an issue if that is the case. If we have the H100i as an Intake instead, and the fans elsewhere Exhausting, this would seem like a bad idea, as the H100i will be warming the main section up, which will be heated up by other components, and because the of the distance between the AIO side location and the other possible Exhaust fan placements, it might create a rather large hot spot inside the case as it struggles with warm air being trapped and heating up components before the fans can exhaust it out. The only real way to know is testing this, so unfortunately unless someone has this case and time to test it out, you'll be out guinnea pig in this area as to whether its a good idea or not.
So looking at that, I would suggest the three fans on the side blowing cool air from the small section on the side towards the middle of the case. The H100i at the top will then Exhaust (blow warm air out), keeping everything inside overall cooler. Assuming you're not trying to cool something the H100i can't handle.
