however, gravity is listed as an element already. if you disagree with his design, take it up with zanz. as it stands, gravity is more or less the 'force element'. as well as the 'mech element', given the aesthetics of many of the cards (and also catapult), however, as others have pointed out, steam machine is in water/fire, so gravity doesnt have a complete monopoly on technology.
That doesn't mean a future world/AU elements could heavily rely on technology - as a parallel example,
Mirrodin is an MTG set that focuses heavily on artifacts (many of them colorless) but also relates to all five colors.
We may not necessarily use all of the following themes but I've decided to compile a list to see what we've suggested so far.
A spell-based element.
A permanent-focused element(s). (Wood, Metal)
An element that focuses heavily on technology/futuristic machines not within Gravity's level of advancement. (Tech)
A direct opposite to Mind. (Body, Strength, Tech)
An element that focuses on stacking. (Strength)
An element that focuses on distribution of generated counters that can double as a quanta. (Astral)
An element that embodies concepts such as kinetics. (Force)
Magnetism
Pursuit of Knowledge
My 2 cents : Themes suggested so far seem to be falling within
characteristics. (Not necessarily a bad thing.)