What if expansions didn’t add +10 levels and just straight went into reputation? Like we go to Zuldazar to get some influence over Zandalari, not to farm +10 levels 
It would require a Cataclysm-alike change of the open world but it could look like so:
- fixed max level
- new fixed 1-max level path for new characters (quicker for alts)
- leveling path is quicker but focused solely on showcasing Warcraft lore, history and how to play the game
- every zone scales up to max level and can be used for current content
- and so each expansion doesn’t have to introduce every tier of crafting items, most could be re-users aside of specialty crafting materials. Existing world could be reused in many aspects
- All the quests and expansions don’t give exp - just reputation for a factions/subfactions, for achievements and what not. There could be even heritage armor sets created for given expansion zones or a zone or a small faction - unlocked by specific rep. Scryers & Aldor and more!
- “old” content TBD if it should be “old” (farmable, low value) or “current” and viable (similar value to expansion, not farmable - running Legion M+ for rewards slightly lower than from BfA M+?)