I would happily fork over cash for ship modifications similar to that used in Star Trek Online. *
Different variants of ships, and you can mix and match to make your own unique taste.
Custom ship HUD's that look totally different from the current one.
Even something as mundane as an apartment on a space station which we can then populate with furniture and other things can be a big investment for Frontier ( ala ESO's new housing system ).
Even without the aforementioned, most of them the kits lack any real imaginative flair; and the quality on some is shocking; one of the kit pieces on the Viper looks appalling. I think Frontier should put a tad more effort into their kits.
* Start @ 2min
https://youtu.be/wM2rY4utKvA?t=101