If they do implement dual type attacks, how would you make it? For me, I would want it to be like two attacks but does half damage each. For example: Muddy Water (BP=95) it would be the same thing as hitting the opponent with a ground attack that had 47.5 BP and a water attack with 47.5 BP. So the BP would be the same on a neutral hit. -If the enemy has flying (neutral water, imune to ground) though, they would only get hit by 47.5 BP (47.5*0 + 47.5). -If the enemy is water (resist water, neutral ground), they would only get hit by 71.25 (47.5*.5 + 47.5) -If the enemy is grass (resist water and ground), the enemy would take normal resistance of 47.5 (47.5*.5 + 47.5 *.5). -If the enemy is electric (neutral water, weak to ground), they would get hit by 142.5 BP (47.5*2 + 47.5). -If the enemy is fire (weak to water and ground), they would take the full 190BP (47.5*2 + 47.5*2). -Although I say I would work it out like 2 attacks, the chances of missing is only once; so while damage is calculated as 2 attacks, the accuracy would remain the same.
By using this method, attacks that have hindering types (such as ground, ghost, or fighting) won't be outright useless against pokemon immune to one of the types. By being dual typed, thus easier to hit weaknesses, weakness bonus would be much lower (x1.5 instead of x2) unless a pokemon is unfortunate to be weak to both types. By this reasoning as well, the same thing has to be applied to resistance.