That is the opposite of how OKW is supposed to be played. OKW has the worst defensive options in the game due to lack of a capable MG, no viable emplacements outside of the Pak43, and the fact that you have no area denial outside of the Schwer HQ (which isn't super hard to destroy). Your supposed to use your trucks as spring boards to maintain constant unrelenting assaults that were your enemy down to nothing.
Unit preservation is everything; you cannot afford squad wipes at any period in the game nor can you afford armor losses. Late game power comes from the efficiency offered by 2 extra levels of Vet not invincible tanks.
I consider a solid forward HQ as the best area denial - especially on bigger maps. OKW just happens to have access on one from the very beginning, non-doctrinal ofc.