Why does this Class not have a Hulked out Form that gets better as it goes up in level.... This seems totally obvious

Am I crazy to think this is that obvious boost this Sub-class needed?

I think thar could be a cool new subclass gaining pseudo rage.  So I do think a transformation subclass would be cool. Full made scientist style. But that's not the alchemist imo

But not for alchemist. Imo alchemist is the utility caster. None of their abilities really imply melee imo. Though green flame with the tool kit is nice except they can't use a shield with the blade for it. 

They'd be good with a few changes imo. 

Give them initial free elixirs equal to Proficiency bonus. 

Give them 2 more cantrips. Or 1 extra and the ability to change cantrips daily. 

Also add more cantrips to the list. They should have access to stuff like produce flame and primal savegey

Give them a philosopher stone. That acts as an alchemist tool and focus for infusions.  It's their item as all subclasses get an item. 

As a bonus action with the stone they can give one person in 30ft the same temp hp as the protector cannon. 

 Change the wording on alchemical savant to allow it to work easier and apply to the healing elixir

Imo that would line up more with being the pseudo caster.

It’s very true that the Artificer desperately needs a “mad scientist” or “mutation” subclass that delivers that feeling of mutating living creatures with concoctions.

The Alchemist subclass we got just didn’t push the concept far enough…frankly, just not that far at all.

I’d suggest the Blood Hunter class for what you’re looking for: the Order of the Mutant provides a much better example of a subclass that warps & transforms a character into an actual brute (among other things).

It’s not close to getting you where you want to be, but Artificers do get Enlarge and the Armor of Magical Strength infusion.  So you can at least hulk out if you want.

You have to combine multiple experimental elixirs to pull this off... drink the Transformation Elixir, now you've grown claws... or giant fists, or fangs, or whatever you want your "Mr Hyde" form to attack with. Drink the Boldness Elixir, you're adding a d4 to every attack you make. Drink the Resilience Elixir, your AC goes up by 1... now you're big, monstrous, harder to hit, and hit extra hard.

So... yeah, it's possible to approximate it, but it's definitely not the best use of your skills as an Alchemist. I agree that there's room for this as a homebrew subclass... Blood Hunter is definitely more deliberately trying to accomplish something similar with some of the subclasses, but I know not every table allows Bloodhunters, since it's not an official subclass and only appears on D&D Beyond because of their partnership with Critical Role.

If you want a Jekyll and Hyde type character, you're probably better off making a barbarian with high intelligence and proficiency with Alchemist's Supplies rather than an Alchemist.  I suppose you could make a barbarian/alchemist multiclass, but I have trouble thinking of two classes that have less synergy.