SSA and courier options

For the last 3 weeks our delivery times have been padded to 7 to 10 days by Amazon when we have it set to 1 day handing time. It caused a huge drop in sales and we dont know why this is happening.

Today I tested the Shipping Automation template and it put our delivery times back to normal.
Now instead of showing delivery in 7 to 10 days , it is 2 to 5 days as it should be.

The problem is it only gives 5 options for couriers with SSA. We use more couriers than this and they are not options for all the ones we use.

Is there a way to enable the extra couriers while using the automated shipping template? Are there penalties for using a different courier than the one provided on the SSA list?

Many thanks