That is one nice point and shoot camera.
PnS are usually made for ease of use or users who don't expect much except common auto features.
I don't own it but looking at reviews I see that:
On manual mode you should have option to select shutter speed from 15 seconds to 1/3,200 second. So at least you should be able to get that 15 second and probably nothing more than that as there is no "B" option.
Wonder if you use +2 exposure compensation, it actually adds to shutter time! Most likely Not.
The easiest answer to you question is that if you came across a situation that mandate long exposure or you know about its existence and benefits, it might well be the right time to upgrade to a DSLR or more manual capable camera.
There might be a possible tweak by booting of the memory card as was with other point and shoots such as S series but not sure on this. Alternatively is there a way to run camera via USB cord from a PC for remote control and extra feature?
Sorry can't think of anything else but to suggest T4i if everything else fails.
