I'm glad to see some conversions are in the works. Lately I've myself been thinking about the clockwork ranger and the coglayer. Seems we've come to some similar ideas for the coglayer. My own thoughts I was working on:
- Steam powers have a complexity rating, similar to spell levels. And therefore, anything a coglayer builds has a complexity rating, based on the sum of the complexity of all its components. Complexity imposes two limits on a coglayer: (1) they can't have more than X complexity in items built, and (2) no single item can have more than Y complexity. For example: to keep Amplifier shenanigans in check, a coglayer can't put all of their available steam powers (or complexity) into a single item. Perhaps a 1st-level coglayer gets 5 total complexity and 3 complexity per item. Then Pilot Light + Nozzle + Amplifier is a flamethrower, and Spark Generator + Amplfier is taser gauntlets. That second amplifier can't be put onto the flamethrower because that's too complex.
- Higher complexity powers correspond to what previously was large combinations of powers. For example, Clockwork Puppet is maybe a complexity 6 steam power (and therefore can't be maintained at 1st level). It functions more like a Conjure [beast, fey, whatever] spell at its weakest, as it has limited power before it runs out. As you gain levels, you could spend other powers to improve its "battery" life to make it work more like a ranger's beast companion or the zombies/skeletons of animate dead.
- Again, akin to spells, many powers have the option of increasing their complexity to improve them. So a bigger/stronger Clockwork Puppet might be Complexity 15 rather than 6, for example. Or a stronger flamethrower could be a Complexity 5 Pilot Light, instead of a Pilot Light + Amplifier. This is really more of a consideration to streamline finding the info you want: each power comes with a list of higher complexity "parts" that actually corresponds to the more common combinations with that particular steam power. Just to limit the cross-referencing between powers.
As for my thoughts on the clockwork ranger - add "gear forest" as an environment. You can give up the ability to select additional environments to gain access to the clockwork ranger spell list, which includes things like Grease, Giant Insect, Enlarge/Reduce (usually used as Reduce for getting through small areas), Wall of Fire, and Steam Cloud (Cloudkill with fire damage). Probably a Repair Damage spell. Mending cantrip, most likely. Include a sidebar on gear forest analogs, such as Ensnaring Strike = Engine Master's Grasp (changing name and fluff without changing the spell itself). With the dropping of 2 Natural Explorer improvements at 6th and 10th level, a slight boost might be warranted, unless the new spell list is sufficiently more powerful. Maybe something akin to the rogue's Expertise, but only applicable to things like repairing the gear forest, disabling its hazards, etc.? Or maybe just a couple extra spells known (you get Repair Damage and maybe Find Traps for free; better if it were Find Hazards). Or maybe just a higher level ability that's like 1/week Guards and Wards, adapted to gear forests. Basically, add a bit of the Hazard Lord path to the base ranger.
EDIT: Got a chance to look more closely at your own work. Good stuff. I'm a little dissatisfied with the steam weapon adept though. Could just be because I love the original PrC so much. In light of how some subclasses (like the Hunter ranger and Battle Master fighter) get to select from further options within that subclass, I feel like that would be the better path to go for the steam weapon adept. And I would miss the clockwork puppet and resultant automatons if not accessible. You mentioned that in 3.5, it took a lot of powers to make a functioning automaton. Well, maybe some 5e steam powers are more complex now. Like, the clockwork puppet steam power basically functions like clockwork puppet + discriminator + animator + automater + whatever else was needed in the past. (Apologies if I've misnamed, missed, or added powers. I don't feel like looking it up right now. You get the point). Basically, add in a tad more abstraction to steam powers, just so you don't need a ridiculous stack of them to make certain applications functional. Maybe mark some powers as more complex, and require a minimum level for use.
Just to compare to my own version I've been brainstorming - I'm not making everything at-will and autoscaling like you. Gadgets (or some official term for items built from multiple steam powers) have limited uses, basically on par with the warlock's spell slots. The limited uses correspond to consumption of power and other reagents (such as a pilot light's fuel), as well as wear and tear before essentially overheating. This adds a layer of tactics that appeals to me, though I'd need to take care of balance: a coglayer could build one very strong gadget, and then be left basically with a standard weapon when it burns out, or he/she could build two gadgets of lesser power, but greater endurance.
I am Omnirahk, half-Rahkshi ("Omni") of the WotC forums. I consider "Psionics in DragonMech" (see my website) my greatest contribution to anything d20 so far. At least, it's my most successful topic.