Im not sure how much itd cost to custom fabricate one of these, but I know that Veilside makes one for the MK IV Supra, and that costs about 2.5 grand. It may be a quicker shift, but it also adds more weight than a regular tranny. Im not exactly sure about your first question, but I'd think that if they have the tiptronic shifter then it should be able to do ok, either that or they'd need to be replacing some tranny's
Mike