I wouldn't call it a pathetic weak design.
I am sorry that you had to put up with this.
There are thousands and thousands of UCEs sold each year (of course, mostly in the Indian domestic market), gear lever popping out is very rare, as far as I know (Please feel free to correct me). It is a big leap to call it 'bad design'. I've had no problems with my UCE since I've had it. It has been 22 months. I'm close to 11,000 miles, I also take care of it like a baby, not that I have any of my own, yet. I do not use it as a daily, and I do not over-stress it.
Few members on here have done close to 20,000mi + without the gear lever popping out, or other major problems. Gear shifting on my Bullet is very smooth, I rarely get any false neutrals (almost none), I keep the clutch play at 3mm at the lever. The bike has always been good to me. It is sad that this hasn't been the same for you.
And I am sure there are many UCEs that run close to perfect, and other members can attest to this. Minor issues, I don't care about them. Japanese precision will never be present on these bikes. The Continental is a whole new breed though, seems quite promising. As this is a forum, people come on here to discuss their problems, which are also present in any other marque, whether it be Japanese, German etc. Nothing is perfect.
Calling RE a POS is also calling the 110+ year history behind it crap also. This is old technology with a modern touch, and the UCE has been a new venture for RE since the iron barrel. Some issues can be expected. I am sure their engineers try the best to keep the problems away. A rotten fruit can sometimes go undetected in a picnic basket. Good dealer prep is also the key, plus owner awareness of their own 'baby'.
The bikes are quite reliable, the bad design is only present in your bike's gearbox/mechanism, unfortunately. Spending $75 in gas to get a second opinion would've still been okay, maybe the dealer could've detected something that your father might've overlooked. Just a few posts ago you had mentioned that the bike is back on the road and then the thing went out again. Now, is this bad design or something that is missing in there, or something that hasn't been looked at properly. That is why I was referring to the dealer.
I can only say good luck...or you might just sell it. It is sad to say, but sometimes Enfields are not for everyone.