Sub-divide then install removable homes

I have a brick house in Brisbane that is on a larger block of land (1095m2). I was advised years ago that the land could be sub-divided. However, the house sits right in the middle of where the sub-division is.

I have checked to see if the house can be moved. It cannot be. I am not keen on developing either.

However, a possibility is sub-dividing then installing removable homes.

Houses like this one.
- Pricing includes delivery and re-stumping

Obviously these houses aren't the best looking but I wouldn't say they are any worse then my current house.

So a breakdown of the plan:
1) Sub-divide:
2) Demolish
3) Install 2x houses a $50,000 each
4) Sell properties. I think $250K each is conservative and achievable.
5) Real estate agent fees: $12,000

In summary:
+$500,000 : Proceeds of sale
-$245,000 : Current Mortgage
- $5,000 : Sub-division
- $10,000 : Demolition
- $100,000 : Install 2 Houses
- $12,000 : Real Estate Agent

Total: +$128,000

Then factor in maybe $20,000 for unknown fees.

Other factors to consider:
- Stumping or slab requirements
- Council and engineering requirements (council requires plans, soil tests, engineer?s reports, photos of the house, payment of application fees, an inspection of the house)
- Demolition approval by an independent certifier (local council can provide a list of certifiers. Certification usually takes around 7 days.
- Tree removal
- Asbestos removal?
- Break out fees from bank
- Re-connecting water + powerlines

Was hoping the forum could help with the following questions:
1) Do these expenses seem reasonable?
2) Anything to add that I may have missed?
3) Does anyone have experience in removable homes?
If you have a mortgage the bank might not like you demolishing their asset AND banks very rarely lend against non permanent homes.
What is the current value of the property as is?
What is the value of the 2x subdived blocks (without houses)?

I cant see any costs included for the connection of the houses for utilities?
What about land works?
Holding costs?

Putting houses like that on a vacant block might actually de-value the property? People will might look at the houses and want to bulldoze them.

Could work regionally, don't know about Brissie though. I'd assume a certain quality of house is expected in the city