The fundamental problem with equivalence principle is, that it's only valid for homogeneous gravitational fields, which are equivalent to a constant acceleration. Real gravitational fields, i.e. fields originating in mass, are not homogeneous, and can only be replaced locally by an acceleration. The whole concept was introduced by Einstein to allow the use of special relativity at least on a local scale in a gravitational field before he invented the concept of general relativity.
Therefor inherently you have to come up with additional explanations outside the framework of general relativity if you want to use a concept like universal acceleration.
And whatever is pushing the earth in this concept, feels an increasing mass and has therefor to push harder to keep the acceleration constant. And any force needs energy and an infinite force needs infinite energy.
And, finally, it is not a god idea to use special relativity examples (constant velocity) to explain general relativity (constant acceleration) scenarios. It is misleading.