On the topic of the pre-mentioned roguelike Adventure Mode, my vision would entail the following:
Branching paths with levels split between text-box interactions, platforming, enemies, Target Test, bosses and rescuing fighters similar to NASB 2
Side-scrolling levels in a similar vein to Melee's Adventure Mode and SSE
Enemies and stat boosts from Smash Run
Spirits to benefit you depending on the nature of your run, similar to WoL
Slowly rising difficulty with the progression through each stage, similar to Ultimate's Classic Mode, except here the difficulty is based on the theme of the stage
The early stages are Beginner difficulty, while later stages rise to Easy to Normal to Hard to Expert