To begin, I have to say, this is one of the most unique of pictures I've seen in your cast of characters and probably one of the most original versions of marriage when it comes to something new and exotic (at least in my opinion). I've always been interested in this whole universe you created with your chars and Im happy to give you my more then 2 cents worth in your pics. Anyhow let's begin!
Vision) A night spacey sky, two lovers locked hand and hand and eye to eye, nose to nose, and with their uniforms on, this clearly shows that Ace and Roz not only have bonded both physically and mentally but the sparks coursing through their hands shows another side that only these dragonroos can understand. Your use of both art rage and traditional talent really shines here.
Originality) Im giving you nearly a perfect score only because Dragonroos aren't just a simple mishmash of both kangaroos and dragons, but it's done to the point where it's easy to see and easy on the eyes as well and this moment of holy matrimony does have hints of say...the movie Krull when the wife tells her husband to "Take her fire.", in this sense, it looks more like Roz's energy is intertwining with Ace's causing the two to bond together until death does them apart.
Technique) Like I said in the intro, your knowledge of art rage really enhances the overall mood and feeling towards this picture and the colors is bright and easy on the eyes and every detail you made really strikes a chord here. You did an excellent job on the technique department.
Overall Impact) 5 out of 5 stars! Not just in the sense that I believe this is one of your best pics so far but your unique talents has a way of conveying more then just two lovers enjoying each other's company as their energies intertwine together but judging by the way Ace looks compared to Roz's, he is in a state of surprise and happiness as he really shows how much Roz means to him and Roz is taking the news with a calm deamenor, which also hints at a flirty side to her.
Idea & Composition: The idea works pretty well complimented by the character symmetry. Their expressions are very natural and the wedding concept you have created is fresh. In terms of composition, maybe adding more width to the canvas can give breathing space between characters and background.
You mentioned attempting to draw with less lines and inking. Some areas work just fine without them while others feel like their lineart were painted over (areas like Coz's ears that transition from lineart to painted only. Consider choosing beforehand which areas should receive proper inking (such as silhouettes and main elements of the body and clothing) and which will work without them (secondary elements such as folds, fur and hair strands).
Light and shadows: There's an intense light coming from their hands and electricity. I think you chose the right areas to bounce light, but rendered it a tad too softly. The further away a light source is from the shadow-casting object, the more you will notice the bluring of light and shadow (What we call penumbra) Here the light emission is very very close to both characters. Even though they are furry, the transition of light and dark should be much more abrupt -Not necessarily a hard "stop" between them, but a shorter transition.
Lighting 2D drawings is very important if you want to properly establish volumes. Be careful with the "embossing-effect" light and shadows can produce inc certain parts. Ace's largest bang of hair looks flat compared to the rest of his face. Though we see lighting, his hair appears to have volume only around the edges.
How realistic or abstract you choose to imply shadow is up to you. Shadow placement can be painted in a manner the general idea of what volume is blocking what light is good enough for viewers to understand.
Character designs are really interesting and well thought (and seem very animation-friendly). Some minor adjustments with lighting will really make your future pieces an extra shine.