Stiffer springs and shocks are BY FAR the best option for what you want. They will limit brake dive and acceleration squat, too. Stiffer springs do NOT make the ride harsher/rougher. High speed compression damping does that, so you need to ask a lot about the new shocks' damping.
Stabilizer bars are at best a tuning aid and at worst a band-aid that limits your suspension's compliance and travel. If you must, change them ONLY in matched pairs. Changing only the rear will give you increased oversteer (tail hanging out) and instability, if you change it enough to affect body roll. Bad Idea.
Mazda installs a rear LSD in Oz and New Zealand. I'm sure you could have one shipped here and installed. Your guess as to the cost.
I disagree. There is no way stiffer springs dont change ride comfort, and you need to properly match lowering springs to a more aggressively strut for it to work, so what you said doesnt work...
Its true that a rear sway bar will cause oversteer, but thats simply not an issue with a stable vehicle like Mazdas. I am an experienced driver, and based on my findings from all my time driving I would happily rather control oversteer VS. understeer. Rear axle drifting is very easy to control VS. Full on understeer, and ultimately you have more control over the vehicles angle via throttle and steering input VS. Understeer, where you have to let go of the throttle and pray you dont smack a curb.
If you are an experienced or confident driver, oversteer without a doubt is what you want. The idea with the rear LSD is a really good suggestion, and I highly recommend that.
But for $500 modifications, youre best off buying front/rear sway bars and some camber plates rather than lowering springs.
I find it amusing that a Mazda fan wants to "reduce roll" in their vehicle.
I find this amusing because #1, the CX5 is already pretty "flat" for a vehicle with 8.5" of ground clearance. #2, the Miata is roll city, and is still the most raced car, and Mazda's claim to fame (aside from a few brief years where they had a decent rotary).
Anyway, you're not going to kill roll in a CX5 without either 1) Lowering it (shoulda bought a wagon/hatch...) or 2) making it so stiff it's terrible to go anywhere in. People can talk about valving and timing and high-speed this and that, but I've never been in a car that managed to limit roll without adding harshness to the ride. Not the M3, not the 370Z, not the Z06, nothing. The ONLY exception was the ZR1 I tracked, with the MRC suspension, but installing MRC in a Mazda would probably cost more than the car is worth once you factor in fabbing/tuning/etc.
Mazda uses a form of body roll mainly on purpose to give the driver a sense how how hard they are pushing the vehicle. Its also partly because they have not advanced their chassis design to a point where the chassis itself can soak up bumps without the need of soft suspension, so body roll is minimal (etc Volkswagen or Acura) Personally, Ive pushed my Mazda 6 sedan hard enough to see lots of body roll (although it was still very composed and controlled) so I can only imagine how much worse the roll is on the higher-up crossover... it does not corner flat despite the fact that its such a stable and fun to drive quickly.
Aftermarket suspension absolutely does not mean that you are going to suffer from a stiff or uncomfortable ride. Bilstein struts are not available for the CX-5 unfortunately, but they offer an excellent blend of street comfort and performance. when you strike the correct balance with a suspension suited to the chassis in your vehicle you will not have a car that rides stiff. The same goes for coilovers such as BC racing. They are fully adjustable, meaning that if you take them to a competent shop who can precisely adjust ride height, damping etc the coilovers might as well just start to ride BETTER than the OEM shocks youve had before.
Funny how you mentioned that the suspension in your ZR1 is too expensive to fit into a Mazda, but were talking about a Chevrolet here... the irony...