I mean, its true that the ship crew rating pretty much stays top notch after you train them up and then stays there forever, which is deeply unrealistic compared to navies that regularly have to do drills to stay reasonably sharp.
Unless you could automate training exercises though, I dont think its a fun thing to add to the game. In reality training is actually an exceedingly costly endeavour for most militaries and choosing to not keep up with training requirements is a pretty common budget decision when times are hard, that could later lead to that military getting its ass kicked. It could be a pretty fun tradeoff (in my opinion) to cut off the training due to a sorium shortage and to then actually feel the negative effects of less well prepared crews. However it would not be particularly fun (in my opinion) to constantly be having to manually re-schedule training exercises lest your fleets become useless.
I'm not sure how much of an issue that would be. If I understand correctly, fleet training can happen at any time while a ship is within the radius of its parent admin command, even while it is executing a movement order, but it needs to be assigned to the training admin command, so theoretically, it would just be a matter of copy-pasting the fleet to the training command whenever you want it on the move, or when it is garrisoned somewhere.
Maybe reassigning command could be an order of some sort? Like, "move to planet X, reassign to TRN Command, start fleet training. If hostile fleet detected, reassign to NAV Command, abandon training." or something similar.
To mitigate the effects, fleet training could decay over time, at a slow rate inversely proportional to the existent fleet training and crew grade. So it might take a year to go from 100% to 99%, another year to 95%, another year to 75%, and then it would rapidly decrease to zero, so a small amount of this decay could be acceptable.
Remembering to assign fleet to fleet training every three or four years is not that big of a chore, unless you somehow have hundreds of fleets.
Yes... it would be a matter of moving the fleet into a training admin after a long deployment or several as you would for the most part not lose that much fleet training. Individual ship experience is completely automated so you don't need to do anything.
If the ship stay at port with a population it would not loose fleet training or individual ship training at all as the ship only swap out crew once in a while. You could just argue that the ships or the fleet will do the occasional exercises and drills to keep the crew up to speed. So this would only impact when large part of the crew have to be replaced after the fleet have been on really long deployments. You would only loose a very small amount of crew points every 5 day cycle, much smaller than you otherwise would. Just like paying supplies for maintenance... you just don't need to have the academy at the local base but anywhere in your empire, we just assume that crew can travel to where they are needed using civilian means.
The reason why it wold work like this is the fact that it certainly is no fun to have to retrain ships just because, just like maintenance. You should only have to care about this if you actually use the ships and need to replace a considerable amount of crew at once.
So I don't think this would need huge amount of micromanagement, especially not with the new fleet training mechanic in the game.
It would impact your willingness to have ships stationed at really long deployments though and building ships that have deployment for 10 or more years will cost you allot of crew points so you will only afford to have a very few such ships... say a few survey ship... you also would not like to loose those ships as the crew is worth allot more to you as they should be with that amount of training they would need for such long deployments..
You could also have a system where you pay slightly less crew point the less part of the ship crew you need to replace after a mission. So a ship that need to replace 50% of the crew pay X amount, a ship that replace 25% only pays 0.3X for example. Which sort of reflect the training that the crew on board the ship can give the new crew. This would make the crew resource something you actually would care about in a different way as your away mission time will impact the cost of replacing crew.
So.... let's say that your empire have a four year crew service length. You might still want to give your science vessel double or triple that while the ships themselves have deployments of perhaps 24-36 months. When they replace crew after a deployment they don't have to pay too much crew points as the initial cost generally is much higher.
Think of crew points more as the cost for you to train and educate new people and not an exact number of crew you have access to. In the "real" world you would have a much better understanding for the exact need of new crew in a way it is difficult to have in a game, so the exact number of crew you have available is not that interesting.. it rather is the capacity to educate them to a certain standard that is.
We also should understand that in today's military ships the cost if its crew generally is the most costly part in money of a modern ship in terms of on going costs in peace time.
