None of the cavaliers can intercept Imeena from M12 (except SC4, who will be long dead).
Imeena will go from 23% -> 13% dodge for one round... in range of two ballistas which do 4 damage each at a 71% THAC0. (48%-> 58% after Avoid/Rescue)
2 * 4 * (58/100 - 48/100).... for .8 difference in damage averaged (with an estimated 3.64 damage unburdened; so 25% extra...*)
Still sounds worth it to me
It will be a 1 turn issue, hardly more severe than surrendering a forested tile.
An unintended perk of Imeena drawing ballista fire may be sparing the more frail Callum from tearing his gown.
*but still weighted under 2 damage, or letting an Archer range on Imeena.