Do you think it would work?

I'm not sure how the unidirectional would behave if the 'back edge' was struck, it might be a problem, it might not. If I was going to include to woven I'd go for a plain weave (it's easier to handle and keeps itself neater); like you say, maybe a woven and a 250g unidrectional with the woven on top. This would make the 'skin' less likely to fracture if a ball did nick the back edge at speed.

For your trimming, just make everything slightly too large and then cut the overhang off with a trimming knife or hacksaw blade once everything's fully cured before you rub the edge back using a sanding block until it's perfectly smooth.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales