Have you tried cutting it down when it gets wilt? It should be cut down at least once every year anyway.

I personally would not replace Jackmanii with a SAC. SAC can reseed like mad and I love the purple color of the blooms on Jackmanii. Does the entire plant wilt or just select stems? Have you checked to make sure that the plant is not being attacked at ground level by something and thereby giving the appearance of traditional wilt? Generally speaking plants outgrow wilt if they are being pruned accordingly and given sufficient nutrients. Have you changed your feeding regime with something that allows a large release of nitrogen versus a slow release of nitrogen?

If all else fails, I might replace the vine with one of the viticellas which are generally trouble free and pretty free flowering plants.