This Datapack with a simple Item Magnet and Triggers To let player Modify their scale.
The Magnet teleports items in a Radius of 7 Blocks to the Player.
The Size Shifting allows each Player to modify their Size.
The Help Page for Size Shifting ( /trigger SizeHelp ) says:
Size Shitfing
Negative -> Smaller (max -16)
0 -> Normal Size
Positive -> Bigger (max 16)
Example:
/trigger Replacement_Size set -11
/trigger Replacement_Size set 7
Adds Commands:
/trigger Magnet
/trigger SizeHelp
/trigger Replacement_Size set <VALUE>
Nothing fancy, should work on Servers.
Disclaimer:
Mincraft isn't made with smaller of bigger playersizes in mind. Some wierd behavior can emerge with very small or big sizes.