Re Alphanum boards: perfect! the same size as the polystyrene marker boards would be good. Could we have left, right, up and down arrows too? I feel those are missing from the types we have in the arrow boards, but maybe they could be shoe-horned into the numbers board?
I've got a whole bunch of other suggestions which I'll save for the future as they also involve type of InSim coding you want to avoid
One thing that can be done with straightforward objects is tall scenery. An autocross layout consisting of only ground-level objects is not just aesthetically limited, the tall things really give you a good sense of where you are on the track, even if subconsciously. Everyone's faster if the track furniture is tall and plentiful around the corners, even the ones who argue it makes no difference
We're making do with concrete sculptures, but they're heavy on the object count and I've seen first hand how people from outside LFS will obsess on the blockiness of these creations and think that all of LFS is roblox-style. (See attached image: much better to drive than a plain layout, but not up to scratch aesthetically)
For example Trees, lampposts, catch-fencing, billboards, footbridges, houses/buildings/fascias, stadium stands, radio towers... literally anything tall yoinked from what we've got already in LFS would be a huge help.