im sorry...
but it will be like a pre season friendlies...many players will be rested and not played in fear of injuries and keen to keep fresh for actuall tournaments such as champions league, premiership, which in terms of money and status will always be more important than what you suggested. Plus internationals which players play for, and this causes enough problems with club and international managers already, which will only add to the problem.
and there is pretty much what you mentioned already, international football, e.g. england v spain, and also club european football e.g. united vs barca, so its almost covered. and theres group stages in europe so there are plenty of games in the season.
however the president of real madrid suggested something similar a few years ago where he would like to see clubs like united, milans, madrid playing more regularly with each other.