Just fyi Riot already stated they wouldn't be doing this.
They decided against a mechanism like this because it compliments a meta game they dont like.
Not sure where the quote is. I think it was in Riots official response to Swaingate.

EDIT: Figure I should have some actual input on changes otherwise.
I like the idea of a hero with so many activate/persistent abilities like you've proposed here but I feel like it could make him almost too OP.
I think Riot could keep him how he is now if they just buffed the numbers a bit. Although a persistent Q is a great idea.

The Ultimate definitely needs some built in defense though, that way we all wont have to build like a tank just to survive through using it.

I think the snare is fine as is since it is a group snare ability, making it pretty invaluable at certain times. If they added a 0.5 or 1 second
Silence I think it would be greatly beneficial to his utility, at risk of making him nearly impossible to lane against (You land a W like that,
run in, EQR and they will take massive amounts of dmg without the chance to deal any back. You back out well in advance before they get
the chance).

whats the **** point of torment as its implemented now? Swain does zero damage as it is... and torment lasts 4 seconds, shorter than even ignite

Best fix for Swain - Make his passive permanent golem buff. Then build tank.

his mana trouble isnt THAT bad

They should make him a true tactician. Give him abilities like "If the next spell the enemy uses is a CC, the effect is reversed" or like "Enemies in this target area with over x% of health take +y extra damage per tick of damage".

how is making torment not amp damage for your whole team not tactical?