I am a WRG2 user also - you should be pleased with them, I think. A winter tyre that is also well reviewed just in wet conditions (deep water aquaplaning aside - as with all winters but a winter with lots of tread is still going to beat a summer with little). Mine are in the garage at the moment as it is so mild and I am trying to use up the current summers as I'll replace them in spring whatever is left on them.
With the amount of old military/walking gear cluttering up my attic (and rarely used these days!) it would be crazy for me not to throw a fleece, gore-tex, small shovel, and so on in the boot of the car. I also keep a compressor, goo, 1l of oil, and a litre of strong screenwash solution in there, plus a small can of de-icer for locks. In crappy weather I add boots and some water and snacks. Might as well - it does not weigh much and like you say there is this space under the boot floor...
Getting a strong enough solution of screenwash into the car in time is always the issue for me. I don't want to be running 50/50 or neat solutions all winter, but here in the south it can go from very mild to very cold then back to mild quickly... I run Halfords extra-strong stuff and have never had an issue IF I get it at least 50/50 in time for anything seriuously cold!