I like keeping things simple but done properly. The standard cast A12 pistons will hold up to heavy boosting using E85.

The problem with the Vitara pistons is they would be down the bore 3+mm. This is not good as you want the squish band on the outer edge of the crown forcing all of the gasses toward the spark plug ready for ign. A piston low in the block can actually promote detonation. They also have a large dish and would work out to be a low compression unresponsive slug of a thing. Id guess it would be about 6-7:1 comp. Easy enough to work out if someone knows the piston dish CC figure..

One option would be to use the Vitara pistons with an A14 crank in the A12 block. A little bit would have to come off the tops of the pistons to get them flush with the block. This would also raise the comp a bit. The A14 crank would also raise the comp(a good thing!).

The cost of getting the rods(pin end), pistons(Crown) and crank(counterweights) machined would probably add $400 to the job. That doesn't include the cost of an A14 crank.

Standard pistons w Good rings, good head gasket, studs and a good tune on E85 it will be reliable, powerful, cost effective and proven.

It is the turbo and Headwork/cam that will make the power not capacity. Sure, a bigger engine will make more torque for a given boost, but turn a few more RPM with the shorter stoke and run a lower diff gear to get the torque back at the axel where it counts. This also takes the load off the clutch and gearbox.