I always used to wonder at rugby/league training what the fuck was the point in "tackle bags" As sprinting then diving full leangth low at the tackle bags was what the coach would bellow at you to do. (And is pretty much the idea you are advocating as far as I can tell). Yet you like literally never attempted to effect a tackle like that on an actual person
And the reason you dont do it vadz, is its an extremely homicidal AND suicidal thing to do. Can you imagine the impact that occurs with two people sprinting and colliding in that manner? How much rugby have you actually played anyway