Go for it, Pondman! Nature abhors a vacuum, and it sounds like you found a potentially good one to fill.
One point, and it's worth making because *not* making it early could cost you dearly: Farm ponds, as in "ponds which are used to support a farm operation", are a completely different creature than what I'll call "decorative/ornamental" ponds. It's true that both are made by filling a hole with water, but that's where it all stops. The needs for each are completely different.
A true farm pond is used for irrigation, water retention (ie, water impoundment) and for the watering of livestock or crops. All other uses (the "pretty-factor") are secondary. Appearance doesn't count. Cost of ownership has to be nil. It must additionally bring to the table a very, very low investment in the way of time and energy, and it must last for years. On a farm or ranch, you have a very tight budget, no margin for error, and you are looking at catastrophe if things get screwed-up. If you have your sights set on farm-pond consulting, you might want to apprentice with one of the "old timers" who does this work and learned it the hard way. The lessons will be priceless. Because farm communities tend to be very tightly knit, one bad customer experience will poison your name for any future work. So you've gotta get it right from the git-go.
I'm betting your current experience is with garden ponds. It's good experience, and it has value within that context, but understand it will not translate into farm ponds. In farm ponds you need to study not only fish, plants and piscine meds... but also how these things will interact with horses, cattle, crops, etc. Example: Put some big lily plants into the pond? It'll make it pretty, but are they toxic to horses or cattle at certain times of the year? Will the pond attract birds or frogs, and will these carry parasites that throw an entire chicken production operation off? How about an algaecide? Or will it kill-off an entire crop of hay and leave the field sterile when the rains come and the outflow hits a field? Maybe use an "eco-safe" blue dye instead... but is it *labeled* for use in water systems servicing food animals? Did you think to wonder if dimilin residue in the runoff from your customers farm pond will whack a neighbors 20 acre mud pond whose cash-crop was crawdads?
Lots of stuff to consider, and until you've been there, it's hard to know what questions to ask. Ponding is tough enough, but when you add the word "farm" in front of it, you've just hit the big leagues.
So definitely go tear 'em up... but mentally draw a line in the sand between what you know... and what you don't yet even suspect. Find an "old farmer" to listen-to, one who doesn't mind lots of questions, and dismiss nothing he tells you until you've tried it a dozen times. (FWIW, this was possibly the hardest lesson I had to learn. Sometimes you'll find that most of the books published by "experts" are useless, wrong, and flat-out dangerous. When it comes to farm ponds, book-smarts is worth *nothing* outside of acedamia. You won't find much of this "high-fallutin" mumbo-jumbo however from an old farmer. Try it and see!).
Best of luck in your new endeavor! Find a need and fill it!
Roark