Oh this one is a lot of fun, I hope it gets picked up.
Seriously? Just off the top of my head there's stuff like:
The MC's and FMC's history together,
Why is the MC so obsessed with beating her,
The FMC chasing the MC and trying to get together with him,
Do the Arrows power stay permanently? Or will the FMC wake out of it,
When will the MC realise his feelings and also fall for her?,
Will the MC feel like their feelings for eachother are fake because of the arrow?,
What's the morality of the arrow and forcing people's feelings?,
The MC's attempts at beating her in archery - and other rival-like acts,
The school's reaction to MC and FMC, don't forget she has a 'fan club',
What does the FMC's job as cupid look like normally?,
What's the MC's background like, what's his family like?,
Similarly, what about the FMC and her family?,
Why are they Cupids?,
Normal school shenanigans like tests, and school trips.
And that's just cliche obvious stuff, I'm sure the author would have some actual character and plot development that would take an entire arc as well.
To me, it seems like it has plenty more to go with it's setting.