Cisco WAN :: 2901 Link To Vendors / How Would You Set It Up

I have inherited a setup for a custom application and would like to know if this is the only way this could be set up.  How would you do it?The application uses dedicated T1 links to our vendors.  There is a Cisco 2901 router in the middle providing the connections.  Traffic to specific vendor's IP's are routed to their prospective connections.  I have attached a network diagram and a config for the 2901.  The way my predecessor(s) set this up, each different vendor uses a different private IP address for the  internal links.  This seems odd to me.  Shouldn't there be a way to have only one subnet on the inside and have the links NAT depending on which route it takes?  The servers have persistent routes built in them to send vendor traffic to the associated IP on the router.  E.g., traffic to Vendor 1 is routed to 192.168.50.1, the 2901's IP address for the Vendor 1 network.  That traffic is then NAT'd to  an IP address associated with Vendor 1's link and the 2901 then routes the traffic to the Vendor's end of the link.
 
I would think that I should be able to revamp this so that internally we're only using one subnet and the traffic could NAT at the link associated with the Vendor.  I recently had to add the 3rd vendor connection, and wound up having to duplicate what was done for the other two in order to get it working quickly.  I didn't have the time to wrap my head around the best way to revamp the whole thing.