I would like an option to choose the level of the 0.5 fight if it is higher than the best for that team.
I have crypt keepers at:
Best Delve defeated 130
Best Delve no casualties 100
Best Delve with faction team 0
I cant come close to beating the delve with a faction team on the lowest level available. It would be nice to choose level 20, 50, 80 or whatever for the faction team.
I If I remember correctly this happened because I did an event first and didn’t have faction troops to try.
It would be great if they let us choose level. For now your best bet is to wait until next faction event to try the faction team as the event always starts at level 20
Or to keep earning treasures and leveling up your hoard until it becomes doable.
I second that. My suggestion would be to offer 6 battle choices for a delve run in place of the actual 3 to give more flexibility to the players.
Lets say you have best delve with free team at lvl 430 and best delve with faction team at lvl 180, here is the improvement: When we select delve, we have 6 battle choices. the 3 with free team at lvl 420, 430 and 440. and the 3 with faction team at lvl 170, 180 and 190. These last 3 will obviously have not only colour restriction in the troop filter but also kingdom restriction to the faction. It will also be of course possible to select the free team run at 420, 430 or 440 and try it with a faction team only.
That would make Delves more enjoyable. Big missing part of this new game mode.
you can normally just wait for an event for that faction that always starts from the lowest level and do that with faction team. nothing irreversible. its actually your own miscalculation of neglecting faction team.
Let’s not be too harsh 
they did mention:
And noob did already mention waiting until the next Faction Event:
It would be nice to be able to go back and retry with faction teams at lower levels. That and MAKE THE FACTION WEAPON COUNT WITHIN THE FACTION TEAM PLEASE!!