Came across this on my journies and thought i would share, though I'm sure many of you have found this already. In each system's .ini
(ie: data/universe/systems/Li01/Li01.ini) there are enties for each debris field,
mine field, asteroid belt, etc. You can easily remove these to remove the field. For example I removed the mine field from around the New York to Alaska Gate:

;original
[Asteroids
file = solar\asteroids\Li01_zone21_mine_field.ini
zone = Zone_Li01_zone21

;edit
;[Asteroids
;file = solar\asteroids\Li01_zone21_mine_field.ini
;zone = Zone_Li01_zone21

I tested this and it seemed to work, but you still get the games audio warning "Danger Mines Detected". Also the zones are predeclared so I assume you can switch positions like putting the mine field where the detroit debris field is:

;original
[Asteroids
file = solar\asteroids\Li01_Detroit_debris_field_001.ini
zone = Zone_Li01_Detroit_debris_001

;edit
[Asteroids
file = solar\asteroids\Li01_zone21_mine_field.ini
zone = Zone_Li01_Detroit_debris_001

This is theory though, as I haven't yet tested this.