Is it possible (and no I'm not doing it myself), to move the main breaker from top left, down to lower right side of this panel, to shorten the wires and clean it up a bit inside? I'm sure it's a stupid question, but I was curious. Thank you.
In order to move that, the new site would need to be capable of accepting a tie-down kit. Not every site is, and back-fed main breakers must be tied down. Also the labeling must be changed to match.
Don't fix what isn't broken.
There is nothing wrong with this panel. OCD can be a boon to electrical safety, but not in a panel so-called "cleanup". That is just uninformed "neat freaking". It's uninformed because there are many better subjects on which to exert ones picayune tendencies. For instance:
making sure every hot and neutral in the panel is long enough to reach any breaker space in the panel, so you have freedom to rearrange as your needs change.
Making sure every screw is torqued down to spec. This is a big problem, that's why NEC 110.14 was added.
Making sure GFCI protection is not done haphazardly (as is often the case), protects everything that should be protected, leaves alone what should not, and is not redundant with some circuits wasting GFCIs and others having too little.
AFCI protection is present where desired and appropriate.
Switches and outlets are screws not backstabs, and are torqued correctly.
Any aluminum wire is on properly rated receptacles and torqued to spec. For 15-20A outlets and switches, that means CO-ALR devices.