you have summed it up pretty well. the receivers that have heat treatment issues and are considered 'unsafe to fire' came from springfield armory with a serial number lower than 800,000 and rock island armory with a serial number lower than 285,000. all remingtons, smith coronas are considered safe to fire along with any RIA/SA rifle above the specified serial number ranges, including the 1903MARK 1, which had some modifications, the most notibale being an oblong cutout along the left side of the receiver to accommodate an experimental system known as the Pedersen Device that would have converted these rifles into semi automatic rifles. the device was scrapped at the end of WWI but the rifles still function every bit as well as any other 1903 variant.
then there is barrel wear, simply shining a bore light down the barrel can show pitting and wear, if those grooves pop out then it's good to go. these rifles are quite accurate by vintage military bolt action rifle(VIMBAR) standards but by today's standards even a brand new specimen that never fired a shot in combat will likely fail to out shoot a MOA guaranteed rifle such as a weatherby vanguard. it's important not to set the bar too high with VIMBARS as it may tarnish your overall opinion and create that little bit of doubt in the back of your mind that can mean the difference between loving it for all time or flat out hating it and regretting the purchase.
hairline cracks in the receiver are invisible to the naked eye, there's no point even worrying about it. there's no way to test for them without risking damage to the rifle and even the test may cause one where there wasn't before so it's just one of those risks that you have to take.
cracks in wood are easy enough to spot and many times can be easily repaired by anyone that knows much about wood work. if you don't ebay has no shortage of USGI stocks available, you'll have to shop around for the correct stock style as their were 4 styles found on the different variants of rifles.
lastly 2 groove barrels. there is nothing wrong with a two groove barrel. every springfield I've ever picked up has had a 2 groove barrel with the exception of national match rifles. 2 groove is the war time standard and almost all that have seen rebarrels were done so with 2 grooves as far as I've seen. a 2 groove is easily capable of minute of deer accuracy which is about all you can expect from any VIMBAR.
Am I missing anything here, I know that Gibbs offers a faithful reproduction of the rifle, using old receivers, but I just like the idea of holding and owning one that may have seen combat. I'd like to be able to shoot it as well.
the Gibbs rifle is not a faithful reproduction of the standard springfield rifle. it's sometimes refered to as an A4-gery as they take a standard 1903A3 rifle, which was the standard WWII issue springfield variant and they modify the bolt handles to allow for scopes. they replace the original barrels and stocks that still hold historical value with brand new production parts and drill holes in the receiver destroying any chance of reverting back to original condition and finish by slapping on your every day leupold/redfield 1 piece scope mount and reproduction scope that is such a poor replica the turrets are backwards.
all of this is to mimic a 1903A4 which was the standard sniper rifle from WWII up until early in Vietnam, these 'faithful reproductions' are nothing more than a 'bubba special' a rifle that before they got their hands on it, had significant historical and collectable value but now as it has been heavily modified has no such value whatsoever.