well your reseller is confused... im a reseller also but in my country and you cant do that...
Because thas how it works... they must be in the same network, in the same vlan...
When you turn an IAP he will try looking for a IAP for a VC(virtual controller), in the same subnet... if he is not able to find one then he will form a new VC. He does this via papi protocol and aruba propietary protocols and this is just done by the L2 network.
Now if you have it in different vlans, or network, then he will be not able to ifnd the other IAP... This is how it works.
They will be 2 differente Virtual clusters...
The only way you can do that would be with a GRE tunnel or something like that in which you can build inside the VPN tunnel and pass the vlan to the other site...