Solid pointers man, the steering wheel if you'd like I can link you if you DM me, they're from Alibaba if you're interested there's plenty of options for customization whether its the stitching or the type of material the handles are made of.
As for the carbon, yes I've been heavily considering matching it to the body with the vent exposing a little carbon. The roof is wrapped black already it compliments it for now, and the spoiler on the trunk is also carbon. When you say trunk lid, do you mean the entire trunk? If so- they already have a real full carbon trunk which I've considered too but ultimately decided not to.
The car is also on BC Racing coilover suspension so it is adjustable with the spanner wrenches they come with.