Having Russia roll through the states of all your principal trading partners is probably no fun.
Adventurism is such a poor take in this case.
Besides, waging proxy wars is very far removed from self-defense.
Building outposts in, e.g., Cameroon to ward against Russian aggression over there is perhaps justifiable in some abstract respect, but it's rather the opposite of self-defense. (Without getting into complicated game-theoretical "we have to stop them over there so we don't fight them over here" justifications, which have long been discredited and have even become something of a joke.)