a) Comparison with previous years will be totally doable. As a quick hack you can simply compare with https://startup.jobs/trends/2017 – but I understand ideally you want the graphs to show the comparison.
b) Jobs by Startup. This is indeed something I'm planning to add to the Startup pages like http://startup.jobs/@carvana
c) I agree salary information would be super interesting. Unfortunately very little of that is public information so I simply don't have it.
d) Data goes back to mid 2016 so we don't have a ton of historical data. But for next year I could look into historical line graphs for top 10 companies.
e) I like the idea of cross referencing sector/skill and remote work. I do have the data to compare e.g. engineering jobs versus communication/PR jobs in terms of remote job openings.
Thanks again!