[Taqwus]

Now, the obvious retort to that is that information on enemy capabilities before and even after contact is made is going to be fairly dubious; furthermore, that some capabilities are difficult to simulate safely.

That would suggest
(a) simulated melee, with minimal lethal spell use, between units one actually has, and

(b) actual combat against target summons that one has little compunction killing -- for instance, summoning Mechanical Men, phantasms, low-level undead, any living units if you're the Ashen Empire... that -would- allow demonstration of lethal capabilities or lack thereof. Done in-game, this would cost resources.

Ex. in-game command 'Stage attack' for a leader, where the mage serves only to direct the target units in an attack but does not actually participate.

That would be fairly realistic, avoids the palette / spoiling issues, and still gives useful information regarding what troops might do (whether they tire too easily, whether they can hit the broad side of a barn, et al)... and, as a battle, it would actually give experience to the units.