[@ProPro] That makes me think of something like detain.

"When this creature becomes blocked, it gets +1/+1 until end of turn. Tap blocking creatures, they don't untap during their next untap."
That's just adding to detain while making it more specific in the hopes to level it evenly.
The block clause is white. The tap clause is blue. The +1/+1 is white and green.
Just an idea, I don't expect it to be taken.