I’m wondering how supplying weapons is supposed to stay clear of Putin’s warning to other nations not to interfere or face instant consequences.
I really don't get people who are naive about Putin. He is extremely clear in his communication about his goals and he just started yet another phase of realizing them. For those won't bother going through them - the goal is pre-1989 setup at least within Europe and near east. All the countries formerly enslaved by Russian communism in some form have very strong objections, and well the rest of free world seems to agree.
Armenia is a member too, but Putin didn't help them in Nagorny Karabakh, saying it was Azerbaijan territory by international law. I beleive it was a demonstrative punishment for Armenian 2018 "velvet" revolution.
Kazakhstan is a member too. Putin used his army in Kazakhstan in January after Tokaev said that protesters are supposedly foreign terrorists.
Putin will not directly help Lukashenko against NATO countries on their territory, but is well capable of throwing his army to "protect" Belorussia from retaliation, including anti-air warfare.