the OP want's a production machine...
he won't get that w/ a HF nor a home made one...
But he never said what he actually will be doing with one, and if using it on metal or wood. All we actually know is he wants it to be used from about 2 hours to 6 hours at a time.
I am personally aware of a contractor that buys HF tools that will be used for basically 10-12 hours a day, 7 days a week. Used like that they last about 3 weeks. Not long you say, but considering the fact that the same tool sold by the name brand companies cost about twice the HF tool, and last about 4 weeks. So, he spends the same amount of money, but get 6 weeks of work rather than only 4. At times HF rocks. I've got HF power tools I bought over 20 years ago, with the idea of buying better when they wore out, or broke. And still use them, because they never broke or wore out.
Personally, I would make one, out of wood. Use it, see where the weak spots are, if any, then make one out of metal, with the weak spots addressed. Then if that worked out, make another, as a standby machine. Then you can do maintenance on one machine, while putting the standby machine into production. Then when that machine needs maintenance, repeat. Should never have any down time that way.
"It ain't what you're told, it's what you know." - Granny Weatherwax
Some days, the supply of available curse words is insufficient to meet my demands.
Call me a craftsman, artisan, or artistic, and I will accept that. Call me an artist and you will likely get a quite rude comment in return. I am not a @#$%ing artist.