I have met Aikidoka who are strong Christian believers but they don't seem to have problems with the bows. Or they hide them.
The quickest and the least low bows are from the people who have no religious thinking and are a bit too self-confident and arrogant. Those saying that Aikido is not about that fancy Japanese etiquette at all. However they don't seem to struggle with their bows - they are quite satisfied with what they have.