Can the Army force you to have more clothing than issued?

Junk beyond the issue items no. However you must be smart on what battles you chose to fight! Anything that is required for you to have is issued. Now, as you go higher in rank things are expected regardless of issues or not.

Another barracks lawyer? The packing list is there for a reason- to successfully make it thru a deployment, mission, operation. Too cheap to but extra- what if there is limited laundry, and your 1 shirt can't be cleaned in time- is it worth an ART 15 for being out of uniform?

It all depends on what kind of solder you would like to be. You can cause friction at every point that is not per black and white regulation, and be known as the boy who cried wolf. Or you can hold out for the big issues that matter, and have your voice heard when it matters.