nothing but cantrips would feel a bit weak it will need something stronger and ideally less spell slot focused?
Nothing but cantrips is an extreme application. You'd have to do the design work to see if it could work, but in theory it can, because spending spell slots is turning the cantrips into the equivalent of full spells. And as for spell slots - they're just a slightly simpler, but slightly less flexible implementation of spell points.
For example:
Telekinesis:
Cantrip
You can use manipulate an object, open an unlocked door or container, stow or retrieve an item from an open container, or pour the
Contents out of a vial. You can only effect objects within 30ft of you and cannot lift more than 10 pounds
At Higher Levels. When you cast this spell using a spell slot of 1st level or higher, the maximum weight of objects that you can lift or manipulate increases by 20 pounds per level and the range increases by 30 feat per level above 0.
In addition you may hurl an object at another creature within 30ft. Choose one object weighing 1 to 5 pounds within range that isn’t being worn or carried. The object flies in a straight line in a direction you choose before falling to the ground, stopping early if it impacts against a solid surface. If the object would strike a creature, that creature must make a Dexterity saving throw. On a failed save, the object strikes the target and stops moving. When the object strikes something, the object and what it strikes each take 1d8 bludgeoning damage.
At Higher Levels. When you cast this spell using a spell slot of 1st level the damage increases to 3d8.
2nd level or higher, the maximum weight of objects that you can target with this spell increases by 5 pounds, and the damage increases by a further 1d8, for each slot level above 1st.
