Wht would 3/4 and 4/4 be easier for guitars and squeeze box than other time signatures or just plain easy for those instruments? The buttons pressed and finger positions made would be exactly the same. The rhythm and accentuation would be entirely in the control of the musician. If you think compound time signatures are hard it's only because you haven't learnt to count them (I can't do 5/8 and 7/8) and once you can do that it's irrelevant what instrument you play them on.