Hey Bernard Guignard, out of the three pictures you have for variants, I like the last one best. Although the engines look small, it kinda reminds me of a Light/Strike Crusier designed for long range based on Excelcior Technology. And with a large aft shuttle bay, could be used for Carrier operations. The smaller warp Engines may produce less speed, but are more efficent (they look similar to Enterprise-A engines only more advanced or require less power) so the overall range of the ships strategic movement is increased.
Just saying I like the last one best.