Even I would love to be able to do it all (as far as gearing up followers goes) with one class I know that I will not be able to, at least at the moment. So below is how I would go about playing the same build you are playing in season. The only thing that is eluding me at the moment is Gloves of Worship.
I wouldn’t worry about the Scoundrel. The only two you need to worry about is the Enchantress and the Templar. The Templar you can gear up using your barb. The Templar is good for speedy GRs and pushes. Where the Enchantress is good for speedy normal rifts and maybe bounties.
So you will only need one more character for the season to be set and it can by any int class. Just play them long enough to get to level 70 and you don’t have to do much after that.
The way I would handle it if I were playing seasons I would first figure out the build. If it is the WW barb then I would just rebirth my barb and one other int class. Get that second class to level cap. Then when farming for the gear for my barb I would use the barb to farm for the Blood Shards, Keys, etc… Then use the int class to gamble for the Enchantress. The follower gear doesn’t have to be the best either. All we need is about 25k main stat total (which is 10k * 2.5 (multiplier that followers get per stat point)).
This way makes it easier than trying to get up all of them. Also I will find ways of using max roll website that tells you how to gear up the followers for the builds that you are using. Where I will only have to have one set of gear instead of having two or three sets for each.