(1) Reserve forces get usually less training time / year.

(2) Reserve forces belonging to a small active force with long-serving (volunteer, not conscript) troops will not be able to draw fully from trained former AC personnel.


Both in combination leads me to the conclusion that reserve forces (or most of them) should focus on not very training-intensive missions.
This in turn leads to my preference for relatively small stand-alone reserve forces, such as a regional battalion battlegroups. Training in larger formations and training deployments to foreign terrains and climates should be skipped until a time of crisis.

Such reserve forces could then augment active forces after a brief period of additional training or be assigned rather auxiliary tasks.

The concept of reserve / national guard brigades that go to war on short notice is for me as great wars-concerned guy (who thinks that small wars are usually a stupidity) simply an unacceptable negligence.