No you did not "pee in my cheerios" friend. Just just stated your ideas and I corrected a few items for which you did not have the correct information about. Granted that in the photos the heated bed is directly on the bed platform so the error is easy to understand that you might think that was the final position. Sorry to say that you are still in error in a number of your statements again.
It is very safe to say that far more FT-5 owners have their printers running than do not. A fast stroll through the Folger Tech Facebook group shows the number of printers producing prints their owners are happy with then not, far out paces those who are not able to print. A small factor of those who are not able to get their printers up and running would be that for many, it is their first ever 3D printer and this means they are still learning the art of 3D printers and printing. This would account for a percentage of their fails.
The FT-5 is NOT by any means a high end printer. But for those who know how to modify it correctly, it has proven to be a very good quality printer for the price and build area. If anyone thinks a $500 printer is going to be good out of the box, they are mistaken.
Sorry but again you are wrong, a completely modified FT-5 with every part I make for them would still be no where NEAR $2500 in costs. For me the costs is almost nothing aside from the material costs. When you own 3 CNC mills you do not have to pay the costs of CNC milling parts. I simply slip my parts in between paying custom milling jobs or run them overnight when the mills would normally be idle. But even at retail costs, the full kit and printer will not cost close to $2500. I have a very successful CNC milling company and make my money milling other parts. My custom 3D printer parts are what i do as a hobby and for enjoyment. I do not charge normal milling rates for them, as I want more people to be able to enjoy the hobby with good 3D printers. We do not claim that just our parts will solve some of the issues people have with their 3D printers. Like you stated, many things go into a more accurate printer. Ditching the stock controller and replacing all motors with high quality .9 degree steppers and replacing the stock hot end with a high quality one is a good start. The FT-5 is a easy printer to modify and this is why I bought one. I know from the very start that I would be changing a great deal of the printer, it is just what I do. I own CNC mills and I knew from the start I would be milling a good number of replacement parts for a printer in the $500 prince range. There are others like me, who see the FT-5 kit as a starting point for a self modified large area 3D printer.
To answer your questions. Yes all the items you are asking about are CNC milled. The braces are a 5083 alloy and the heated bed is a 7000 series alloy.
To answer your issues with the t nuts. The issue with T nuts is as you state. they suck... They do not like to turn and engage and often like you stated, care must be given to make sure they engage. One issue with the stock braces is that their thickness of 6.4mm is too close to the thickness of the screws which they use. This means that the T nut sit too far forward on the screw and are pulled too close to the 2020 to allow the free movement with ease they need to fully turn and engage the channel correctly. We addressed this by slightly recessing the screw holes to allow an extra 2mm into the braces, which then pushes the T nut an extra 2mm into the channel, thus allowing the correct space for the T nut to swing into place without hitting the 2020 channel before rotating into the correct position for engagement.
With the extra 2mm recess, one just has to simply push the screw into the recess which in turn pushes the T nut deeper into the channel to allow it to swing into position when a fast twirl is given to the driver. This makes it far easier to put the printer together.
Yes putting a guide on the braces might help to line the frame even better but as you mentioned before, prince point comes into play. Producing the guide, tapped the hole for it and inserting the guide all take time and add to the cost and for such a small benefit. The idea behind the CNC milled braces is not to claim they make the printer square and 100% lined up. They are produced as an alternative to wooden parts which can, swell in high humidity areas, break when stressed to far or when the screws are over tightened. As the brackets are face milled to within .005", they serve to bring the front of the frame flush and it is up the customer to align them in the vertical plane.
Another possible solution would be to use longer screws to replace the stock screws which are too short for the given application. But this causes two issues, 1: the cost of the replacement screws for either us, thus driving up the cost of our parts to the customer or for the customer to have to source them on their own. 2: Longer screws would have the risks of marring the inside of the channel as they bottomed out on the wooden braces.