[Adapted from a comment I made at William Wildblood's blog:]
There is no problem about believing in agency and the Omni-God - so long as agency is really believed.
The problem with the Omni-God concept comes (and this seems to have happened in many times and places, and to be a tendency in many denominations - Catholic and Reformed) when Christians in practice value their concept of God's power above the absolute requirement for free will/ agency.
And then they move Christianity towards conceptualizing Christianity (and Christian societies) as almost wholly about obedience to rulers/ rules, submission to divine (and/or church) authority, and a conviction of life as ruled by fate/ predestination.
Such people lose sight of the fact that it is, and must be, a personal choice to follow Jesus Christ.
One cannot be a genuine Christian without a solid and in-practice belief in the reality of agency.
The other problem is those people who are prevented from becoming (or remaining) Christian by their conviction that it makes no sense to insist on both an Omni-God and free agency.
Because, as Francis Berger says in the comments linked above: The perceived power of God is largely a matter of speculation/ rationalization, but we experience free will and agency as personal and real.
I want such people to know that one can be a good and real Christian without regarding God in that power-defined way.
In other words; one can be a good and real Christian while regarding God as The Creator of this world - but neither omnipotent, nor a creator from nothing.
In yet other words; I am engaged in making space for a different kind of Christianity that is expressed in terms of different metaphysical convictions from the mainstream and traditional.
(Convictions that which I also happen to believe are true! Or true-er - at any rate.)