So far we have been using the BP numbers in cm. I would like to reduce those even more. My infantry battalions are 9cm wide (two 45mm stands). Assuming musket range was not much over 150yds, and a typical battalion frontage was about the same, I think maximum musket range could be about 9cm. Range modifiers for muskets could be eliminated to simplify firing. Movement would be reduced in proportion. We will probably play the rules as written for awhile before tinkering.
All of my other figures (15mm, 10mm) are on thin bases, and I agree with you that they look better. I selected 1/8 inch thick bases for the 6mm since I was worried that my (old, clumsy) fingers would damage the figures if I could not get a grip on the base. Time will tell if I made the right choice.