Yes please!! A few different themes would be ideal (i.e. Light, Dark, Black)

Or perhaps if you were going to do a full overhaul of themes (🙏) - take some inspiration from how Slack implements their theme options. For example, offering a few simple pre-sets - with the ability to tweak and customise them (so they can be aligned with the brand colours if desired)

A simple Dark Mode would be plenty though, if a full overhaul is too much!