I would not agree to reserve football only on a Friday night, it would cause too many problems.
Saturday would suit or Monday evening might be a possibility.
The problems with a Friday night match would come about where panels already train on a Friday night (due to players working or studying away during the week).
They could no longer train on a Friday night due to the reserve games.
If the reserve panel are away on a Friday night they would have a max of 15 seniors at training (more than likely less than that). If the club has only one pitch this again rules out training on a Friday night when playing a home game.
If the match does go ahead on Friday night the senior management will not see the game if they are training the senior panel.
This would also mean the reserve players would only train once a week
Does that not also rule out Monday nights?

Anyway, semantics and aside, I think Fionn / CL / TB are onto something. This could potentially give a lot more football to a lot of players. the promotion / relegation element of it will make it more competitive and the timing (allowing players outside the 12 to be available) will up the standard.
18 guaranteed games run during the summer months on top of whatever Reserve championship / occasional senior league and McElduff cup appearances sure beats training 2-3 times a week from Feb to October for 10-12 games in the current format.
IIRC there was some lip service paid a few years ago to bringing in non-competitive or casual games to increase participation and allow those who could not commit fully to get a bit of football. This could also go some way to addressing that need.