Offline mode only mod out for D2R named “Better SP” at nexusmod. Does almost everything I want and they will be adding more features.
Features so far:
Way larger inventory, cube, stash
Increased run/walk speed
Lowered stamina drain
Mercenaries can equip more things (gloves, boots etc)
Item levels are visible
Skill max levels are increased from 20 to 99
Removed experience gain penalty from higher levels
Hell Countess can now drop all runes
Increased high rune drop rate
Increased mob density
Increased drop chance for items
Runes are now numbered (El (1), Eld (2) etc)
Tomes and keys stack limit increased to 50
Arrows/bolts stack to 500
Increased Hell Act 5 area levels, they now go from 81 to 99
Hell Cow Level increased to area level 99 (you can still access it anytime after killing Hell Baal)
New cube recipe for unsocketing: Scroll of Town Portal + Socketed Item = Item + Socketables --- Unsockets items without destroying runes
New cube recipe for full respec token: Scroll of Town Portal + Scroll of Identify = Token of Absolution
Ability to use all skills in towns (some get visually off though from town protection)
Andariel drops are always quest drops (Andariel bug, no longer have to manually bug her for better drops)
Planned features:
Infinite ammo on quivers/throwables
Perfect gem drops in Hell difficulty
Immunity removal (although i've heard that D2R vanilla already allows piercing through immunities)
Ability to use any or most skills from either side (auras under left-click etc)
Move-only skill
Something similar to Melee Splash mod (not sure yet, how to approach it)
Increasing maximum character level
Plugy-like respeccing of stats/skills
Ability to toggle features in .ini file like was the case with many mods in original D2 (trying to find, if someone has managed to make this functional)
Make numbered runes support all languages, currently they have number only in English version.