hello my fellow geeks.

I've recently started running this for a new group who are used to other systems and a definitive answer to dice rolls.

now with this system being as it is atm all they consider using threat for is the standard of strain and I want to spice it up to make them think more .

Any advice for this

How the threat is spend is your call as the GM. Also the spending threat table in the book is a very good orientation but also suggestion, you can spice it up however you want. Of course within reason.

Players can choose how to spend Advantage though.

Use threat as setback dice, they don't have to take it as strain after all?

'They' don't get a say if you don't want them to. The GM by default is in charge of the interpretation of Threat and Despair on all dice pools. So you get to be 'the spice'.