Sharing grounds is the most untenable idea there is. Without even going into the dynamics of different clubs working together (which is 0% chance of success), there purely is not enough space/time in a week to share a field.
If it's a match day venue only, possibly.
But clubs struggle to find room for teams to train as it is. If the quality is to improve across all football (which is what we all want) the players need to be on the field more often, not in the corner of a field more often.






