Personally i am extremely enjoying my experience on osrs however there are a few things from rs3 i miss and would love and some might surprise you.
1. A money pouch to this day i still keep forgetting to withdraw my cash and i'd actually love one in OS.
2. Dung, I'd camp the fuck out of this if it came as a minigame/skill
3. Chaotics ^
4. (Future) Down the line say a few more years i'd love if they introduced some version of overloads and extremes
5. Divine
6. Pvp armour #Memes
so what would you like in os or rs3 A few things from myself when i played rs3 would be:
1. Osb - Ability to price check items anywhere + An easy xp Trackers
2. The house upgrades ( Pool, altars, jewellery boxes etc)
3. Slayer bosses
4. Zeah - Focused slayer area