I am not a mortgage broker, but Chris Berry is and he might be in a better position to help you understand what is, and what is not possible with loans.
I would suggest for your consideration a few items to review:

• undertake due diligence about the purchase and subdivision before proceeding incase you are not able to do what you think can be done. A pre-application meeting with council on the subdivision aspect and confirmation in writing from the council would be a must for me.
• Legal advise on the purchase with another person to ensure any issues, or if something was to happen to either parties involved in the purchase and what is the best entity to purchase in to avoid double up costs.

Cheers,
Jason

It’s probably best you talk to a few financial people like an your accountant, your mortgage broker, and a financial planner to understand your specific circumstances.
They will be best placed to give you information on the pro’s and con’s of each option
If you don’t have a mortgage broker, Chris Berry from find a better rate is really helpful

cheers,
Jason