For what it's worth.

Years ago Dad bought a pull type bale wagon when they first came out. After I saw how it worked it was the greatest thing since sliced bread. The two issues I hated was the small stacks it made and the long time it took in road work.  You mentioned having to travel 2-3 miles from field to stack.  You will eat your back tractor tires up fast that way, and it will still take you a long time to run that distance. Depending on your traffic conditions it's only maybe 5-7 minutes run time with a self-propelled wagon. I can run 45 mph loaded easy,, can your tractor move that fast?

I'm not sure what you call too much of an investment in a balewagon,, but your time, tractor and health issues are a consideration.  I did a quick look on ironsearch,, http://www.ironsearch.com/IRONSearch/details.aspx?IWNO=1042116&rowid=24DD51CB-8E30-4630-B820-BA8343458471  and found this 1075.  Possibly it has already been updated to a 1085 computer. The 1085 computer allows you to build any kind of stack you want, including squeeze blocks that can be mechanically stacked into barns.

If you bale 5000, 50 lb/ bales a year, that would be about 125 ton right? You mentioned if you automated you could easily jump to 500 ton/year.  It looks like doing the math,, you would be much farther ahead financially to get a good used 1975 or 1085 and increasing your production.  Labor would be 1 baler driver and you running the balewagon. I only bale 3 twine so I couldn't tell you how many 2 twine bales you could put on, but depending on your 2 twine bale weight, you should be able to get 4 ton/load. 2 loads an hour running 2-3 miles depending on your traffic conditions and stacking conditions.  If you don't know, the 1075's, 1085's are 2 ton ford trucks with New Holland sheet metal on them, and the Perkins diesels are fairly bullet proof, easy on fuel, thou not a powerhouse. Don't buy anything with a straight 4 speed/2 speed. Gearing sucks on the 4/2's.

As far as breakdown's, Operator abuse is the quickest breakdown activator there is. Not paying attention driving into holes, road ditches, too fast on bumpy ground and they will start breaking frames, springs, axles etc.  I climb hills you would NOT BELIEVE with the 1075 picking up bales going both up and down hill. Yes, I have spun the tires and broke an axle, but it's only a 3 hour fairly simple straight forward task to replace an axle. Having seen what happens to a sloopy axle switchout ( not checking for broken pieces of axle and having the entire readend "eat itself" with broken axle pieces)  I simply pull the other axle- pop the driveline pull the ring/pinion gear bolts- replace 4 of the bolts with 12 inch bolts slide the rearend out (hanging on the long bolts) take a magnet pull out all the little pieces, and slide the rearend back in, replace the axles, done.  Unless you are hauling hay in the extreme conditions I do, I doubt you would break an axle. I also have rill irrigation which means a ditch every 34 inches which I doubt you have.  I've never broken the frame, and only had 1 spring set break.  There is more little maintiance and greasing every few hours is important.  But,, compared to having to have 3-4-5 people handling hay by hand,, and more importantly just finding people will do the work, a balewagon is allot less hassle.

As was also pointed out,, if you're having labor problems, chances are very good other hay growers are too.  If you are putting up 3 cuttings a year?  at 166 ton/cutting, you'll be hauing hay about 20-21 hours. Factored on your 500 ton/year.  That would be maybe 2-3 days tops,, which would leave you time to pickup some custom work-off setting the purchase price. Just looking at the situation from clear across the country,, it looks like maybe 2 weeks a year custom hauling would about pay for the machine?

The other issue is the customer angle. If they leave the hay in the barn anyway, cut the bales and only take out what is needed to feed their animals,, the bale weight isn't any issue anyway.

IF I were a hay buyer instead of a producer,, I would not buy hay strickly "by the bale" period.  I would want to know the number of bales in a ton or price/ton. I do sell hay to small quanity buyers and I've been asked the "per bale price" sooo.. I take the ton price and divided by the bale weight or bales per ton. I normally make bales 16-17/ton.

With the other systems you've mentioned you are still highly dependent on labor and/or extra machinery to get the hay into the barn.

again, it's just my 2 cents,, but I would seriously consider going the self propelled 1075-1085 option. And having the option of delivering directly to the buyers, and having your own hay barn.  IF you do go to a regular balewagon hay barn,, get PLENTY of rock under the thing, and gravel over that, (in my area most all hay parns either have asphalt or cement to set the hay on) and get the floor of the barn well above the surrounding area. Think about the worst winter and rain conditions and build to meet/exceed that possiblity.