So I was browsing through some rosters and noticed some teams with National team players who are being over trained. The teams that I was looking at were clearly not doing it deliberately, however it dawned on me that it is now possible to buy up NT players, change their individual training intensity to something that reduces their energy levels and effectively ruins their usefulness for their WC campaign.

Suggestion: Make it so that you can't change training intensity for NT players to anything higher than 'Average'

The easiest solution (if it is a problem indeed) to exclude the energy level factor from WC matches), and assume all are playing at 100%.