Could a creature have both Deathtouch and Poison/Infect. Would the rules allow it and would this add flavor to future cards like {Pit Scorpion} or {Sabertooth Cobra}? (Example: Creature does lethal damage to other creatures, but players take Poison Counters) Also, could you add Deathtouch to a Poison creature, via an Enchantment, Artifact, Soulbond creature like {Nightshade Peddler}?
Yes they can have both.
{Tainted Strike}