the water turret in vanilla is unlocked right away without research.
for A.P. coal an steam it would be great to place it after "Fluid control 1" + "military"
(the modpack has two new science packs [Industrial science pack and Steam science pack] fluid control 1 and military are researchable with the "Industrial science pack" as the water turret should be too.
The "Industrial science pack" is available right from the start, so there's no technology to research it. I could add a new technology and set "Fluid control 1" + "military-science-pack" as prerequisite for the new tech.
Thinking some more about this, it would allow for a kind of tiering:
- Shoot just cold water -- could require "Fluid control 1" + "military-science-pack".
- Use steam -- could require "Water supply 2" + "military-2".
- Use hotter steam -- could require "Nuclear power" because only this will give you hotter steam.
It may interest you that I've already figured steam temperature into the damage calculation for the next version, so hotter steam will indeed cause more damage than the 165 °C steam you get from normal vanilla boilers. :-)
for the recipe:
8x Mechanical relay
12x Pipe
5x Gearing
1x Basic machine frame
That's already implemented. I haven't played in expensive mode yet, but I guess I'll use the expensive recipe you suggested. If it doesn't work out, somebody will complain for sure! :-D
It will still take me a while until I can upload the next version because I'm still working on the fire-extinguishing logic. But it will come eventually …