Glad to see that myself and CJF did not run you away from your own thread.
How large of and area do you have that you consider as available space. The only constraints as to what can be done are your imagination, space and your bank account.
A couple of things that I would recommend that you keep in mind with any expansion or addition if it is to accommodate fish.
1. For your climate, a minimum depth of 4 feet is advisable.
2. If you have Koi, plan on a maximum stocking level of one fish/250 gallons of water. This is another debatable guideline. Some say 100 gallons per koi, while some of the hard-core Koi fanciers will advocate 1000 gallons per Koi. Generally speaking you don't want to overtax your available biological conversion (filter) nor do you want your fish to live in stressful, tenement house conditions.
Whatever you decide, we will try to help. Who knows, once you learn enough, you can be the Pond Contractor for your area, since there is not one within 200 miles.