First off. Razorback Spam lists. Grey Knights can do this well. Its just so cheap to get your razorback when you have 4pt Warrior Acolytes. Give them either storm bolters (huge net rage atm alongside PsyBolterBacks), or up to 3 meltas in there. Space Wolves who were by far the best at Razorback lists, now have a new challenger when it comes to these style of lists. Personally I think Spacewolves still do it better, but that is not the purpose of this article.
Lets step back. Looking at this unit, the first thing I notice is that the guys really have no armour save although they can (3+ invul with Crusaders). They also can carry a large number of special weapons. Warrior acolytes can carry 3. Jokaero's are special weapons, and Inquisitorial Servitors can be included with up to 3 special weapons.
What I see here is the chance to utilize the chimera in ways we have not really been able to before. 5 possible special weapons shooting out of the top fully utilizes the top hatch of a chimera. While Veteran Guardsmen could get up to 4, it was not as efficient.
The first opportunity I see here is 3 inquisitorial Servitors with Multi-meltas. Plasma Cannons are options with a nice range boost, but lets face it, Grey Knights lack any real melta options (they still have no problems with armour, but melta additions are nice).
I have 30 custom battle psykers already. It takes 8 of them to make their large blast S10 AP1. This fills in that chimera nicely with 11 models, leaving just enough room for Coteaz. Note that other inquisitors can take special weapons, so if you are going this route, you have a 5th weapon option already.
I know that the Psykers are fickle. In fact, I had a chimera the other day with only them in it. They periled and immediately their heads exploded in round 1. Not to mention that the double ones I rolled was wasted, due to a nearby librarian. However, a S10 AP1 large blast at 36" cannot be ignored. My suggestion, put some warrior acolytes in there as well, so you do not lose the entire unit when they implode. The mess insides that chimera is horrible.
Since Servitors really work in the Inquisitors unit (they require one or mindlock possibilities), any other additional Henchmen units I have been setting up with 8 pskyers, and 3 warrior acolytes with meltas. Add in a single Jokaero if you have extra points (i don't).
This makes your henchmen a fickle and yet deadly possibility on the tabletop. Your chimeras can move forward with any venerable dreads, and fire away as they go. (i use rhinos on their side armour). A move 6 fire 36" large blast template is fun. If that doesn't work, you still have 3 melta guns to run around with. The funny part, is how many times my purifiers have jumped in chimeras to make some distance.
I have been fielding 4 chimeras alongside my Grey Knights. This likely will change, as the army gets more efficient, but I am fielding a ton of S10 AP1 large blasts, alongside lots of melta and mult-meltas. The problem of course and why most people are ignoring the chimera as a viable transport is that they do not come with fortitude. However, 5 shots out the top I think makes up for this. Not to mention a chimera can still be equipped with a Warp Stablization Field if you are going that route.
There are other options with henchmen as well, and some extremely good ones. I will get to those another time. The Chimera above in the pic was done by Dio´Ra. Pics are somewhere on Warseer if you are interested.