I'd really like to see some real flowing water being able to be put in the base. Waterfalls, standing water squares. Even if they are bought with the new system in Freedom. I'd also like to see new base decorations just in general. The ones we have are old and although creativity plays a part in base designing, you can only do so much with what we have.
Most importantly, waterfalls (could be hung as wall items) along with outside fake windows to give a sense of location, as well as flowing water squares and standing water squares.
Also, manual option to turn on some base defenses, like the arcane ceiling item that kinda looks like a disco ball.