Weapons wielded in two hands have advantages and disadvantages. The obvious disadvantage is that it takes both hands, thus preventing use of a second weapon or shield. Against missiles in particular this can be perilous. The advantages with two handed weapons are their reach, WSB, FV and the ability to use full weapon EL vs ALL melee opponents to their front (not just put towards a single opponent or split between opponents as with one-handed weapons). The same amount of EL applied defensively towards one applies to all melee opponents. Further, leverage allowed by two-handed use means that weaker people can use the weapon (at WSB-1). Thus while a Bastard Sword WSB+1 requires a SB of +1 to use one- handed, someone with SB of 0 can use it two-handed. Similarly a Great Sword WSB+2 only requires SB+1 to use as it is a two-handed weapon. A Spear WSB0 can be used two- handed by those of SB-1.
NOTE - Other options thought of and rejected were applying EL twice (at full offense and full defense), applying full EL twice towards all melee opponents and using any special rule vis-a-vis shields.