The waterboy Alchemist

But if you start feeding Ag's early you suddenly become this hero with a sup-bar stun, and a little bit of minus armour, whose game contribution just kinda stops.

It's why I'd say I agree with Hamster's idea of heroes you'd have for Ag's upgrades, ones where the Ag's is amazing, but you just don't have/don't want the slots for it. Not on Heroes like Tiny or Queen of Pain who like having early Ag's (Like first item Ag's) because they buff your farming speed. But I think it only works when you've got like a mid Alchemist who functions as a 1 position, and you use the Void or Jugg as your late game carry when Alch starts dropping off.

I still think he's too weak as an offlaner to be viable in that role. He's squishy, and even with Acid Spray, zoning him is decently easy (There's also no way he can contest last hits in an offlane position. Like, if creep equilibrium is controlled, if he goes forward to CS he dies against any relatively strong safe-lane tri. (Maybe it'll work against some of the weaker ones, but you really don't see weak tri-lanes drafted a lot in this meta)

If it's a strong trilane he can just go stack ancients and clear them with Acid Spray though, and come back to annoy the carry when he sees the 2 supports rotating.

WIth the ancient camp it's pretty much a guaranteed early Maelstrom no matter what you're facing. And even then you can spam spray on the enemy carry so he won't freefarm.

What about a #4 Warlock that transitions into a #2 or something? Again, he just needs REfresher