Any suggestions would be welcome.
Without any details of what you are asking the Contractor to do it is a bit simplistic to say … but I will have a stab !
In broad terms, pure housing i.e. no civils and other infrastructure, is pretty simple work and easy to specify, so the best thing the client can do is specify it and any constraints well and then get out of the way of the Contractor. This lends itself to an option A contract.
In terms of secondary options, I would expect at a minimum to see :
X1for inflation if the contract duration is over 2 years;
Either X4 Parent Company Guarantee or X13 Performance Bond
$180 million dollars sounds like a lot of housing, so you probably want it completed in sections, so X5 sectional Completion.
X7 Delay damages
Possibly X16 for retention.
However, I am worried that you are going into a $180m contract asking such a rudimentary question. PLEASE TAKE PROFESSIONAL ADVICE from someone who can advise you well !