Are there any cases in which you'd get a blazer tailored to be almost one size smaller?

The background: As part of an attempt to freshen up/upgrade my wardrobe, I recently picked up a Rag & Bone blazer, I think from winter 2012-2013 or fall 2012. I've been trying to wear more blazers instead of cardigans to work and felt a need for more spring/fall-weight blazers, and I also wanted to add more variety, as the majority of my blazers are either solid or a tweed (maybe a glen plaid, pinstripe or understated houndstooth if I'm being especially daring). This one was an absolute steal at Saks Off Fifth, but it was also one size larger than I usually wear, not to mention the fact that it's not petite-sized for 5'3" me.

There would certainly be precedent for tailoring it down -- Kelly at Alterations Needed actually had some dramatic resizing done to the same blazer a year ago (see before and after pics). In my case, since I usually find jackets a teeny bit snug in the bust, you could make the argument that I'm buying to fit my largest part and taking in the rest. The risks are that a tailoring job might not turn out well and that if I decide soon that I don't like it, all the tailoring would make it harder to consign/resell. That's a consideration because the pattern is a bit bolder than my usual style (I tell you, I'm very boring); perhaps I'd be too timid to wear it.

So I'm torn. Do I keep it, or is it too much of a risk? Do I do some trial wears before getting it tailored (so that I can consign it if I don't like it), or is it sabotaging the test even before I start because I'd be wearing something with a suboptimal fit? Is it not good/current/flattering enough, and am I being blinded by sale goggles? (I'm betting that even with alterations, it would still be a bargain, especially as there are no shoulder pads to move and the sleeves are unlined, simplifying the job.)

More generally, I guess I'm asking, how *do* you decide when a garment is worth extensive tailoring?

(Although I'm too shy to post WIW photos, I'm actually putting up a few photos of the jacket for those visual types. Now excuse me while I run and hide...)

#1: The front view, unbuttoned. (Please excuse the blur; I didn't realize until after I downloaded the photo that I must have been in motion when the photo was taken.)
#2: The side view. A little poofy over the rear view...does that bother anyone? (And please excuse both the blur and imperfect pants length in this one; these are new shoes and I'm just testing them out.)
#3: The front view, pulling the shoulders in a bit to sit closer to where I imagine they ought to be.
#4: The front view again. This time I pulled in the front panels a bit at the center, maybe by 1/2", to approximate a better fit.