The devil is in the detail, and as far as I'm concerned, first you'd have to explain what you exactly mean by mineral/energy focus or rather, how you want to implement them.
As it is right now, I don't believe you can make a discernible distinction between mineral or energy focus. Sure Yang and Domai favour industrial output over energy, and Morgan under Demo/FM/Wealth can rushbuy things like crazy, but apart from that, factions need both decent production and decent labs, both provided by boreholes.
Also, part of the game is precisely finding balance between your treasury, lab output, industry and army. I'm not sure if I want to be forced to choose which leg I stand on, I'd rather exercise both.
Last but not least, I don't have this impression that fac hurry cost is too low. But that may be because I try to switch the slider to labs as much as reasonably possible and I'm usually quite poor. :) Sure buying rectanks is easy, but tree farms and hybrid forests are everything but cheap.
Basically, it's a question of what terraforming you use. Mineral focus means you use crawled mines and worked forests and boreholes, energy focus means either you use solar collectors and echelon mirrors (possibly with terraforming to raise the land in question), or go for crawled nutrients and get specialists.
Ah, that's the thing. There's no question that if you switch to labs as much as you can and focus on energy you'll have infrastructure problems. The problem is that it's possible to go pure energy in your terraforming, put economy at 40% or 50%, rush buy all your facilities, and have better facility production and better research than the guy who goes labs as much as possible and relies on minerals for infrastructure.
Well, I don't think my terraforming is in any way unusual, and even with energy-oriented factions I can't say I discern any 'focus' here. Basically, I start typically with 'forest & forget', sometimes I add a farm or a mine/rocky, but that's only because leveling down rocky tiles is a waste of formerhours. Then of course boreholes on coastal tiles and condensers for specialists. One thing - I rarely use collectors and never make echelon mirrors. You can always raise some terrain and put more boreholes there.
I believe there is an optimum way of working your territory and it has nothing to do with any kind of focus. Use your improvements where they're most efficient, simple as that. Focusing on either mins or energy is suboptimum.
Actually there is a question. By moving the slider by 10% in the midgame, you change your income by several tens ec. For this you can buy only 2 building turns at a good base. You're slower with tech and you won't make up for it just by throwing cash at infrastructure.
To be honest, in the games I play, I fail to see the problem you see. Even when playing at Demo/FM/Wealth I can't just rushbuy things like there is no tomorrow.
How much do you earn midgame?