Update. I've got a small city almost through Dwarves, which I started after the changes took effect.
I built 10 granite mines and 4 copper mines. Leveled the granite TOO fast and had to work hard not to cap out early on (but did not). Leveled copper slower, but ended with everything at level 4.
I'm finally about to be techlocked on the last row before the AWs. I've filled them all and unlocked the most expensive one, and now went back for an optional expansion tech I skipped at the end of ch5. I'd skipped a few optional techs to keep myself out of techlock later and have been successful so far. I still haven't taken the optional SS tech in ch6; if I do that, I might avoid techlock altogether. A few of these late techs require copper but no granite, so I wish I had a 5th mine but I'm not gonna build one at this point. If I'd leveled them as fast as I leveled the granite, 4 would probably have been right. Early on, a few more granite mines at lower levels might have been easier on my coin/supply coffers; I went close to broke leveling granite mines too fast.
I've sorta-targeted kp in event chests, have bought some with surplus coins, and have had mostly 1000-1800 pt tourneys in there, so some kp above the daily norm (and all 24 daily accumulation) but I haven't been what I'd call aggressive about getting through the chapter.
So, 10-12 granite and 4-5 copper mines should allow a player who logs in frequently to completely avoid techlock (and occasionally scramble a bit to get enough kp, lol). Players who don't mind a bit of techlock can obviously get by with less, and of course YMMV on anything.
Just wanted to share my experience.