When the panic started to subside, I purchased a couple of lowers for my sons (oldest was 2 at the time, youngest was still in the womb).  Prior to the last election, I purchased lpk's, bcg's, and Pmags for their future builds figuring that these are all of the common parts that could be hard to find if things went south (i.e. Hillary).  I figured that I would wait on the uppers, so they could choose what they wanted, but now that AR prices are at an all time low, I'm rethinking this.  While handguards, muzzle attachments, optics, etc change with the times, is it safe to assume that your basic 16" midlength barreled upper will be "future-proof" (i.e. not old school/obsolete in 10-15 years)?

Along these lines, I'm considering purchasing a couple of PSA 16" mid, 1 in 8 stainless freedom uppers for $169.  I figure that I will remove the classic handguards and shave the fsp's.  The boys can pick whatever the new wiz-bang handguards are in style when they are old enough to build them.  Good plan?  Are these barrels worth a crap?

I don't think anyone can answer whether the system will be "future proof" as it really depends on what new things come out in the future.  For $169 each it's not much risk I suppose, but I wouldn't recommend shaving off the FSB or anything until you're sure that's what they want (and then you can do it together).  Keep in mind that stainless steel can still rust, so storage and maintenance will be something you have to consider.

The only thing I could add to your question would be to consider the exact same NITRIDED-upper from PSA instead of the stainless (PSA SKU 516445740 $159.99). Nitride should be as corrosion-resistant but might be more "durable" with regards to long-term barrel-wear from use and storage.  

I'd personally go with the same nitrided PSA Carbine-gas M4-upper, but that's my particular quirk.  Good luck.

I've bought stripped lowers, parts kits, BCGS and PSA nitride pencil barrel uppers for my grandkids.  The lighter weight rifles will make it easier for them to learn to shoot.  I figure the AR deals will be gone by this time next year.

Why remove the handguards and sights?
Who knows if M-Lok, keymod or even picatinny will be around in 15 years? Look at the retro forum. Old school has stayed cool and even gone up in value. I'd buy some kind of PSA upper and throw on DD A1.5, matech or usgi carry handles.
Also I'd buy some usgi aluminum mags. Pmags are great, but I don't trust plastic 100% in the long run. Don't put all your eggs in one basket.

I've got two gov profile mid length uppers with fixed FSBs and removable carry handles for my two sons. They're on 80% lowers with collapsible stocks. Eventually I'll get around to etching the lowers with their names and birthdates. 

Once they're old enough, and have proven they are responsible enough, they will get them and can modify them however they see fit. If nothing else they have a good base rifle to build off of. Of course until they are 18 I'll say yes or no to the mods they want. I don't want them wasting their money on garbage. 

. They reach 8 or 9 have the. Start buying parts in there names. While they can't buy lowered they can buy 80% receivers. Can kids build their own guns?  Idk. But kids are capable of great detail.

You should have bought them Garands.

Any particular part or parts assembly could become hard to find in the future. So why not have ALL the parts to build the rifles? Buy a kit or all of the parts assemblies and tools to complete the rifles. Don't forget spare parts as well. IMO you should have several more lowers on hand. What about your potential grand children??
Don't forget ammo for the kids and grandkids.

In my view the way to future proof a weapon kit is to build it and test it.
Maybe when the time comes you will be able to ‘modernize it’.
As popular as the platform currently is I would like to think there will be plenty of options 10-15 years out, but I can’t see that as being guaranteed.

This. I'd say get irons on it and test fire now to make sure you don't have a canted fsb or anything. Find out now, not in 15 years!

A properly nitrided barrel would be significantly more corrosion resistant and more durable than bare stainless steel.

Any barrel properly taken care of with low miles on it will outlast most all of us. Worst case scenario it'll be called a retro.