It's probably also worth noting that ANY army can pillbox in woods if the terrain happens to be favourable- so this isn't purely a WE problem.
Possible alternatives should probably revolve around ease of perfect wood placement, or the escalating benefit of multiple forests.
Some examples:
-An "I place, you place' system. The WE player would place the first forest they've bought, the opponent gets to place the second, the WE player the third, and so on. All must be placed in the WE board half.
-Post-placement scatter- as it sounds, after all bought forests are placed scatter them 4D6cm in a random direction. They stop if the hit other terrain, a board edge, etc. You may want to let them cross the half-way line, and could have an 'annihilation' possibility- A forest hitting another forest removes it from the board, with no compensation (or opponent places as they want anywhere then scatters). It'd discourage over-foresting a table and placing bought forests too close to each other.
-Scaling cost. Each forest costs the sacrifice of a number of Wardancer stands equal to the number of forests already on the board. Ie. placing 1 forest on a bare board costs 1 stand, a second forest costs 2, etc.