Are you talking about a redraw arrangement or refinancing?
If redraw, then just do it.
If refinancing, I think this comes down to purpose of debt. On your numbers, the $110K you borrowed for your IP was for investment purposes. If you transfer this equity to your PPOR you are using money you received a tax deduction for for non-deductible purposes (or something like that – my brain isn’t working on the detail).
It might work if you effectively sold and bought the IP and refinanced that way, but you’d be up for stamp duties on the transaction.
You will need to be able to prove whether the plants are more or less repairs / maintenance (deductible) OR whether they are improving the value of the property (capital works) (offsets capital gains).
Get some advice from an accountant. If you are using SIS’s, best get advice from two.
Didn’t API recently publish a report showing the “worst house / best street” hypothesis actually has legs, mainly because of the location factor.
If you have any eye at all on CG (and who doesn’t) then remember that there ain’t a lot you can do to improve the worst street, but there’s a lot you can do to improve the worst house.