TS seems pretty adamant on a power house MPV for trackdays. Well if u must, this would be easier done with the Exora. People are already dumping serious power into em, gsr conversions, evo conversions and mivec 1.8 etc. But if the only reason you wanna track an MPV because its your family carrier i suggest get an mvp and keep it as a family carrier. Then buy a cheap second car to play. Heck even a proton saga would work. you can play with suspension upgrades and stock engine. Chances are it is still better then a family mpv on track as you will be able to have a proper suspension set up instead of something with a comfort priority.
Hmm...I drove Alza for four years and I honestly hate the handling and chassis. It feels like I could twist the chassis when I went into corner too fast. Surely you need better suspension system, gearbox, strut and anti-roll bars, etc, to make it work. Might as well buy second hand Toyota Wish and mod it, and not many modification is needed for Wish compared to Alza. Toyota Wish got lots of potential, for a balance between family car and for enthusiastic driving.