Would it be a much of a hassle to add auto-upgrade or manual upgrade to turrets since higher marks are now straightforwards upgrades?
I don't know that they'll always remain so (making the energy cost not completely flat, to give a reason to use lower mark ones, etc), and in any event since the caps are not mutually exclusive (like harvesters) I don't think it's really a fit.
FYI, 7.042 will probably get out noonish tomorrow (Wednesday); I made progress towards it this morning but I won't be done with it today.