Another idea - who owns IP 2?
If wife or you and wife consider borrowing to buy wife's share. Interest could be deductible, minimal CGT (?) if she has low income. Proceeds used to pay down PPOR.
stamp duty exempt in Vic.
Tax consequences mainly.
If you pay your cash into a loan and later need it you would have to reborrow it. If you reborrow the interest would not be deductible unless if was borrowed for investment or bsiness purposes.
You just need to do some spreadsheets and run scenarios
Have you considered selling the shares you own outright and using the proceeds to pay off the PPOR loan and then buy back th same or similar shares in wife's name.