Thanks for your kind replies - I'll try to answer each one of those.
@Zygmund, the "Leonardo" model is a beautiful one, but it is kinda "oldhammer" for me: I began collecting my Empire Army during the 6th edition, so I'd prefer to maintain the newer style - however I'll look for him! I already have a metal Hellblaster from the 6th ed., but the plastic one (even an Hellstorm Rocket Battery) may satisfy me in terms of kit bashing, the same as the plastic Steam Tank (my engineer commander is a bit stiff).
@The Black Knight, I bought from them the "ulrican" captain and I was satisfied, but their engineers, while they can be a fine addition to my army, do not express the "steam-punk-ness" that I'm looking for. Concerning Gamezone, their minis are spectacular, but I prefer their halberdiers or captains.
@Midaski, you are right. Owning an Empire Collector's Edition (pdf, sadly), I was able to search for a suitable model, but I wasn't so much fascinated - the metal ones are fine, the plastic ones are very customisable (I kinda assembled a Master Gunner for my Cannon Crew), but I was looking mainly for a miniature following the principles of WYSIWYG (in my armies, the engineer is required to man the Hellblaster, so no weapon required). I was awestruck by the artwork depiction of the 8th edition Army Book Engineer (
https://i.pinimg.com/originals/d6/61/e5/d661e533298e2e0c3861ce697822ce0a.png) and its richness in details: I saw that newer Sigmarines (Lord Ordinators -
https://www.games-workshop.com/en-GB/Stormcast-Eternals-Lord-ordinator-2018, Celestar Ballistas -
https://www.games-workshop.com/en-GB/Etb-Stormcast-Eternals-Celestar-Ballista-2018, etc.) are covered in details, so maybe kitbashing is the way, but they are often composed by a small number of bits, too bulky to be simply put on the table. The same applies to Karadron Overlords models (from the Aether-Khemist
https://www.games-workshop.com/en-GB/Kharadron-Overlords-Aether-Khemist-2017#utm_source=Warhammer%20Community&utm_medium=Post&utm_content=AdepticonReveals28032019 to the Aethiric-Navigator
https://www.games-workshop.com/en-GB/Kharadron-Overlords-Aetheric-navigator-2017, even the main Lord
https://www.games-workshop.com/en-GB/Brokk-Grungsson-Lord-Magnate-Barak-nar-2017 is full of trinkets and assembling possibilities).
I also visited Privateer's Press, Mom, Norba, and so on, but the perfect engineer keeps evading me.
I'll continue looking - thank you for your great ideas!