The other thing to remember is that we have a number of action cards that can now be played without actions. I built a highly effective engine in one game with Displace/Sheep dog/Falconer. I got to use Way of horse, find my Displace to gain either a Sheep dog or a Falconer.
In spite of having exactly one action, I nonetheless, was building a full engine.
Likewise, you can build a surprisingly effective engine off Gamble with the right cards (e.g. I powered up Animal fair, bought plats, and then piled out). It would be even an even stronger option with Delay out as well. Certainly something like ultrathin Goons/Treasure/Gamble would easily crush BM-Goons going for provinces.
Delay also merits special notice. If buys and draw are cheap enough, you can easily set up an engine of something like Council room/Terminal where you begin each turn with 15 cards, play a single terminal and then delay your other 2 Cr to do it again the next turn. Obviously, if you have non-terminals, this gets even easier.
I could be wrong, but I think Menage is going to be more engine friendly than most of the original block of expansions.