Yes. I was one such designer. You could do a UI in Flash and then export all its animations to cryengine. The actual design tools in Flash were mediocre, but some animators really loved them. For designers, it played well with Illustrator... if an illustrator vector file updated you could re-import it and reuse the animation. You'd just draw your UI gizmos / HUD / whatever, assign anything to be a sprite and hook it from code. Any complex vector animations could be created visually and then triggered. It even had full 3D capabilities, worked really well on mobile chipsets and could leverage a GPU, although in the UI-as-export for games context it would run on the CPU.