The scenario "Last Flight".

What prevents you from simply not using the 3rd tier? I personally just gathered everything together for convenience.
Where can I download these scenarios for 3.1?

By the way, I also, when playing through the entire campaign in 3.1 with the new neutral creatures, rarely used the new neutrals before the Tribes of the East campaign.
Regarding the scenarios, I don't know; I play in the regular versions.