I'm sorry but I fail to see how the Master X buildings are for builders, or designed for builders. They may be in theory but in practice...
The way I see it, there are four possible "builder" victory conditions - in that you can win them with a minimum of warmongering.
Altar of Luonnotar: Not going to be wanting engineers this way except maybe one to rush the final bit - every not GP you get slows you down.
Cultural Victory: Seems way more related to great bards - and way more useful to get them for their massive +12 per turn or +4000 once culture. This line is filled with Bard buildings anyways (drama)
Religious: Hard to get without doing some warring to handle refusal to convert, but I imagine with OB and disciple spam and LOTS of tech-trading for quick religious swaps, you could do it.
Tower of Mastery: You're going to be going up the mage line. The mage line is filled with sage buildings. You don't need Great Engineers for anything beyond rushing the final tower (which, you can also do with 400 slaves

trust me on this.)
None of these victories seems to scream Great Engineer. What the GE screams, to me, is the style of "build up and have a big war" builder, not "peaceful building until the end of time." The two buildings that give out GE points are on the Smelting tech and the Construction Tech.
Smelting is notable for being on the way to Iron Working, a "stab that guy" tech. Construction is needed for catapults, making it, to me, a "take that guy's stuff" tech.
I build a lot of actual buildings as compared to troops - Money Changers, Harbors, Granaries, Theatres, and whatnot, and tend to invade with a small stack of highly promoted units I've codled from the ground up. Isn't that what the great engineer Master buildings are supposed to be for?