add a 5th depth to S5.
what? did you expect something else?
this would lower S6 by one floor, thus increasing the radiants. you can leave the mission untouched: it would be in line with T2 bosses and it would add something to the arcade. it would also make S6 drop radiants all the way through instead of starting one depth after its start.
I like
though I wouldn't call it a full fledged fix to the radiant dilema