After messing about with spawning witches and creepers for glowstone, redstone and additional gunpowder, i decided that the MFR grinders weren't working fast enough for my needs. Mobs would build up in the killing chamber far too fast.
It was then that I switched to autonomous activators, with 1-shotting cleavers with fortune on them. I found that while it took 150mB of mob essence to spawn a mob, I could kill one and harvest around 420mB. Straight away I realised that I could instead be powering my reactant dynamos with mob essence directly, and blaze powder as the solid fuel. This meant only having to spawn blazes for both my needs.
So, here's my current setup (which btw isn't fully at its maximum capability. Even running an MFR laser doesn't have the blazes spawning non-stop)
1. Spawning Room
This is the spawning room. It has a full floor portal to catch any/all mobs spawned. It could be much smaller if it were to be dedicated just to blaze spawning, but i also need it to potentially spawn other mobs, endermen for example. Each spawner has power feeding from a dedicated and switched energy cell above, with a tesseract supplying mob essence below. Levers and lights above for override/show spawning. To the right you can just see the edge of the killing chamber.
2. Spawning Control
This is the space above the spawning room. Each auto-spawner has its own energy cell which I turn on and off from a central control room depending on what i want to spawn. There are lights and override levers near the camera which are available from underneath.
3. Killing Chamber
This is the killing chamber. Mobs drop from the portal block above into the 1x1 space. This could be located essentially anywhere, but I placed it where it fit. Start at the purple block at the back, thats an entity detector which will turn on the autonomous activators (AA) when a mob is in range. There are two AA's, each with 2 cleavers assigned as per pic 4. One sits in the activator itself, while the other is charged and ready to go out of the Energetic Infuser beneath it. A sequencer sits on top, set to around 5 minutes which via 2 pulse formers and repeaters set to 2 ticks alternatively empty the used cleaver from the AA, sending it to the energetic infuser for recharging. Meanwhile, the ready-charged cleaver automagically gets pushed into the AA. This ensures minimal downtime (a few ticks). Mobs drops are sucked up by the vacuum hopper, with a sewer sucking up the mob essence, both of which are sent via tesseracts into the engine system. The item ducts that pull the cleaver from the AA are set to blacklist stone, and the other 8 slots of the AA are filled with stone to prevent the other cleaver prematurely entering the system.
4. Cleaver
Cleaver. Manyullyn Large Sword Blade and Plate, Obsidian Tough Rod for the Reinforced III and Paper tough rod for writable. Add diamond and gold block, and netherstar, and load it with lapis for Fortune III, the RF upgrade for recharging it, and lots of quartz for sharpness. These do the trick.
5. The Reactant Dynamos
96 in total for a total of 7680RF/tick. The system can take some more but i kinda ran out of room unless i force load more chunks. Basically the mob essence comes in to the tesseract above the tanks which is part of the control system. Blazes will only spawn when that bottom tank isnt full. The bottom tesseract feeds the mob spawners and the dynamos. Blaze rods come into the system at the very top tesseract where they sit in an MFR deep storage unit (DSU) before being fed into a pulverizer. Blaze powder is then round-robin fed to the dynamos. Excess sulphur is pumped back up to sit in one of the other DSU's up top. They hold things like brains, muscles, enderballs, gunpowder, redsotne etc from various other potential spawned mobs. Anything not matched goes into the chest at the back so i can see if i need to deploy another DSU.
6. Control front side
The other side of the system. Main storage cell which feeds the rest of the base. I have a comparator on that so that the engines only start up when its below 80% or thereabouts. This saves them running all the time when not required. The conduits are hidden behind panels, but it effectively goes Blaze rods in DSU -> Top of Pulverizer -> Blaze powder out the sides (sulpher out the rear)
7. Control system
Can see the tanks better in this shot. Comparator from them into MFR cable. Also comparator from storage cell into same cable on a different colour. Levers are overrides. The illuminator is actually hooked up to the control channel for another storage cell which directly drives the MFR laser underneath this room. The laser only runs when the main storage cell has over 40% power or something. I was getting sick of messing up a small detail and having the laser drain all the power. Actual control is done using an MFR PRC, only simple stuff like greater than and less than are used, but that's all it needs.
And that's about it. I do need to expand the room a little, i'm not sure how many more dynamos I can run, but it might be another 16-32 or something.
Let me know if I need more detail in any particular area.
Hope its useful.