I've used the search button to find a variety of good options for those who wear holsters; however, I would like to solicit thoughts about the drawbacks (and advantages) to non-holster options.
I'm in San Antonio, which means that much of the year is warm or hot. Therefore, wearing a jacket or blazer probably isn't a good solution. Even a windbreaker would look odd on a 95 degree day.
A large, loose shirt might work in conjunction with a holster; however, it seems likely that drawing a weapon might take a considerable amount of time as I lifted the shirt, drew the weapon, and tried to avoid getting tangled in the excess fabric. Various "fanny" packs are available, but look like what they are - an attempt to hide a firearm.
I would like to find a solution that conceals, is convenient, but is not obvious. Ankle holsters would have me attempting gymnastics while in a stressful situation. Amusing to observers, surely, but probably not a good solution.
I prefer a full sized automatic - probably a Glock 22 in .40, or perhaps a new HK USP in .45, just purchased as a result of studying this forum

Neither of those seems easy to conceal in light clothing - which, in my case, normally consists of a knit polo-style shirt and dress slacks.
So...would a small messenger style bag work? On the positive side, it would conceal effectively and provide adequate space for a full-sized frame. On the negative side, it would be subject to theft (a thief might grab it in a surprise attack), it would certainly take longer to draw, and I suppose there is always a risk of leaving it lying about. (Yes, that would be stupid, but I think one must allow for the possibility). I thought about an inexpensive laptop case, but that might increase the likelihood of theft. Other solutions, such as the Versapack, look too much like places to conceal weapons. The camouflage pattern would have an effect opposite to the original intent, and would, I suspect, draw attention.
Any guidance would be appreciated.
Nmap.