The restriction of upgrades to facilities based on the level of other types facilities can be removed. Stadium size, scoreboard, utilities and parking size (most have a part to play in revenue) have nothing to do with pitch, medical and training facilities (that have a part to play in injuries, training and recovery).
A team with stadium size of 10000 places can have a good pitch, good medical and training facilities.
stadium size is related to the number of fans in mostly the region (revenue)
utilities are related to the number of fans in the region (revenue)
parking size is related to the number of fans attending matches in the stadium
scoreboard is related to the size of the stadium
pitch quality is slightly related but not restricted to the stadium size
training and medical facilities are independent (training and recovery)
'under 21' development is independent
Upgrade restrictions should only be applied between facilities that are closely related.
The title that I wanted to put was: 'Remove The Restriction On Facility Upgrades To The Level Of Other Non- Related Facilities', but the amount of characters that can be put in the title section is limited.