In my opinion, to avoid all the hassle and cost for transferring of the property ownership (since the property is also charged to the bank), it is best just to have both your aunt and uncle to give you (or whoever) a Power of Attorney over the house and/or ask them to sign escrow the Memorandum of Transfer form with love and affection transfer.

You can practically do anything with the PA. It can safeguard your interest and deal with any problem arise from the property in the future.

Only when the property is fully paid off (discharge from bank), you can transfer the property by using the PA and/or the MOT.

However, the issue now is the mental situation of your aunty. As far as I know any form of contract signed by any individual with unsound mind is not valid. Best if your psychiatrist can prove your aunty is of sound mind when she signed anything, otherwise it would be difficult. But then, if there is no one to challenge the transfer in the future, life goes on. However, lawyer might have a way to work around this issue. You have to consult a lawyer about this issue.

Anyway, the above is only my opinion.