They don't have to strictly be as weak as half a skill prof (so about a language or tool), I would argue they be about as strong as Expertise (makes you considerably better within a restricted niche you have already committed to). Which would equate to roughly one bullet of your typical 3-part feat.
Agreed, we don't want the tricks to just add onto the typical routine and become just as boring as 'I attack', which is presumably what this is all to combat in the first place. Oh, movement is a possible avenue we can use as a resource substitute as well.
Situational is good, I think enhancing actions that typically aren't competitive with 'Attack' such as Search, Dash, Use Item and Help are a good start. There is also extra synergy if you can take those actions using something like Cunning Action, Haste or Action Surge.
So to propose some tweaks and additions:
Acrobatics:
+2: Standing from Prone doesn't cost you extra movement
+2: On your turn you can use 15' of your movement to increase your reach by 5' until the end of your turn
+3: Attempting to escape from grapples and effects that cause you to be Restrained use your Bonus Action instead of your Action
+4:
Athletics:
+2: Your shoves can push a creature up to 10', and if they cannot move the full distance because of running into another creature or surface they take damage equal to your Athletics roll (categorized like fall damage so isn't subject to bludgeoning resistance). 15' at Prof bonus +4, 20' at Prof +6
+2: Your movement speed is not halved for carrying a grappled creature. At prof +4 it isn't halved when dragging either.
+3: Jumping only expends half the amount of movement of the distance you travel
+5: You can attempt to bend and break Force effects such as the bars of a Forcecage by making an Athletics check against the Caster's Spell DC.
Arcana
+2: By spending a short rest with an item you can identify it as per the Identify spell
+3: You can substitute an attack (like a shove) to instead attempt to disrupt a spellcaster. They must make a concentration saving throw against your Arcana check as the DC.
+4: You can substitute an attack (like a shove) to instead attempt to hamper a creature's magic resistance. If you succeed on an Arcana check against the creature's spell DC any advantage on saving throws or damage resistance against spells are negated until the start of your next turn.
Medicine:
+2: When you expend a use of a Healers Kit on a creature that creature also regains HP equal to your Medicine bonus (stat + prof)
+2: You can attempt to use a Healers Kit on a creature to poison them, forcing them to make a Constitution saving throw against your Medicine check or be Poisoned for 1 minute. Cant retry on creatures that make the save.
Perception:
+3: When you take the Search action one creature you can see cannot become hidden from you until the end of your next turn.
Insight:
+3: You are always aware of when you are Charmed or having your thoughts read, or otherwise being mentally influenced.
Intimidation:
+2: You can substitute an attack (like a shove) to cow a creature that can see and hear you, forcing it to make a Wisdom saving throw against your Intimidate check or be Frightened of you until the start of your next turn
+3: Successfully Intimidating a creature renders you immune to the Frightened condition for 1 minute
And so on.
How many skill tricks to aim for? I think 6 for each skill, with 2 to start with at the +2 prof bonus stage but it could be hard to put that together.