Does anyone here know of a conservatively gassed or at least reasonably gassed midlength 14.5 or 16 barrel that comes with a factory A2 FSB?  I’d like to find something, ideally light weight profile, to shoot most often suppressed but not always.  I’d be fine with either chrome lined or nitride.

You can always get a restricted gas tube if too gassy.

They don't offer any lightweight profiles (the "lightweight" contour they sell is really just a Gov-A2 profile), but Centurion Arms should fit the bill beyond that. They list gas port sizes on their website, so you can check if they work for you. They'll drill + pin an A2 FSB on these barrels as well for an additional fee.

Another company with a very good reputation for barrels is Sionics. I recently ordered a 12.5" midlength from them, and had them drill + pin an A2 FSB as well. Unfortunately, it looks like the price for the service has increased substantially from when I had it done though, more than 2x as much. The Sionics barrel is very reasonably priced though, so that might help offset some of the FSB install cost.

Wild card option: buy this stripped PSA URG with a midlength FN CHF barrel with a pinned FSB for $430. Consider this: Centurion CHF barrel = $300 + $95 fee to pin an A2 FSB = $395 total. But, for just an additional $35, you can get the PSA FN barrel with a free upper reciever, A2 flash hider, and classic round handguards included! Not sure what gassing is like on these however,  especially vs. the Sionics and Centurion options that have a reputation for good gassing.

This is really helpful.  Thanks for providing all the info and links!  Appreciate it.

There's a blem version of that PSA upper right now as well, $339.
https://palmettostatearmory.com/blem-psa-16-chf-midlength-5-56-nato-1-7-upper-without-bcg-or-charging-handle-26409b.html

Damn, that’s a great deal on a CHF barreled upper.  I wonder what kind blemishes can be expected in this upper?  Is it safe assume they are just cosmetic blemishes and nothing that would affect the reliability or accuracy of the barrel?

No problem! One thing I forgot to mention if you go the PSA URG route, and you plan to pull the barrel from the upper (either to swap barrel nuts for a new handguard and/or to install in a different upper) is I've heard some horror stories about PSA upper barrels being torqued to gorrila-spec levels. I have no experience personally with PSA uppers, and that very well could just be an internet myth, but if true, could be a possible pain point if the barrel needs to come off.

Three other barrel options to add:

1. Noveske, if you don't mind spending the $$$, had a FN CHF barrel with a pinned A2 FSB that may meet your requirements.
2. On the other end of the spectrum, looks like Balastic Advantage will pin an A2 onto many of their barrels for a fee.
3. Finally, you can get a midlength Daniel Defense 16" CHF barrel with an A2 for $316 from EuroOptic here. It's a standard Gov-A2 profile though, which I personally am not a fan of, but beyond that, seems like a very solid choice.

Also, not sure what the gassing situation looks like on any of the above three options either.

Spikes use to make a light weight dissapator with mid length gas. AIM sold them.

I had one long ago and sold it. I’ve regretted letting it go ever since.

Green Mountain makes a few really nice barrels which you can have a FSB added to separately, and their prices are quite reasonable for the quality that they provide.