You have to engage your subcontractor under what you consider to be the correct set of rules of engagement for them to fulfil their obligations and meet your required risk profile. I would generally say you would use the Supply Contract and either amend it to a subcontract version, or have a statement that where it says Supplier it means Subcontractor (or Subsupplier?) and where it says Purchaser it should read as Supplier. You may also need to change some of the timescales so they have less time to do something so you have their submission before you can add to it and submit up as your submission (e.g. period to produce a compensation event quotation you need quicker from them to produce your own quote). In most instances you want to be back to back under similar terms/rules.
I do take your point here though that you feel the Supply Contract was not the right contract. If for your example your Subcontractor is doing an element of supply AND install, then you may well be correct that you should consider using an option A contract down the line even if you are under what you consider to be the wrong type of contract. The important thing is that either way you will be back to back under an NEC type of contract, so language and principles will all be similar.
I do take your point here though that you feel the Supply Contract was not the right contract. If for your example your Subcontractor is doing an element of supply AND install, then you may well be correct that you should consider using an option A contract down the line even if you are under what you consider to be the wrong type of contract. The important thing is that either way you will be back to back under an NEC type of contract, so language and principles will all be similar.