Really? Unheated mason jars won't work? I'm a newbie and completely uneducated but it seems mason jars would work, in regards to the seal. I've used them for storing miscellaneous things through the years (other than canning meat in them) and many times when I go to open one there is definitely a seal on them...either a gasket seal of sorts or a slight vacuum seal.
When corking a wine bottle with a natural cork it is understood that the aging process incorporates an exchange of gases and oxygen. So, if the mason jar leaked a tiny bit of air (in either direction)...well, so do corks. Besides, the heating of mason jars in canning is really different than storing an alcoholic beverage in them...deadly bacteria such as E coli is a reason for the heating beyond the boiling point. High-acid water bath canning depends primarily on the acidic environment to control bacteria. The vacuum seal is to insure no outside, possibly deadly, bacteria enters the jar. With wine the acid range easily falls within the range of water bath qualified vegetables and fruits. With the wine's acid content along with its alcohol content it seems that it is somewhat self-preserving, better than water bath canned vegetables even, other than the vacuum seal. Corks don't create a vacuum...except momentarily when you remove them from the bottle.
In my area I've seen everything from shine to wine in mason jars. Maybe what I have experienced has not aged for ten years in the jars, but there again I see corks advertised as only being "Good for 2 years". When we age in a 1-gallon jug with an airlock on it, there, too, we don't have a heated/vacuum seal. I guess it might depend on the length of time you're planning on bottle aging.
The one thing I would be concerned with is the much wider air/wine contact area in the jar compared to a bottle. But, as for seal itself, I'm not looking for a vacuum.
Just my two cents worth and definitely subject to ridicule, correction, slaps on the wrist, accusations of blasphemy, and agreement.