Your idea has a similar shape and design to what I currently use, except mine has mosquito netting, descent ventilation, and is easy to get in and out of. By the looks of your drawing, you want to have the ends closed up while the shelter still has a floor as the same piece. Currently made tarp tents need that gap near the ground for ventilation, otherwise you suffocate. Even with limited ventilation, silicon nylon is very waterproof. Your condensation builds up quickly and then rains down on you. I have experience trying to use silicon nylon as a floor, and I've got to tell you that it doesn't work well. It's too slippery and you'll be sliding all over the place while trying to sleep. I learned these things using a Integral Designs Silshelter with a Silponcho for the floor. With that design, It looks like you either have to have a guyline on each end attached to a trekking pole to keep the tent up or have a door on each end halfway closed and staked down there. The latter will make it harder to get you and your gear in and out.
My current setup is a Integral Designs Bug Tent and two Integral Designs Silponchos. I sewed velcro to one 8 foot side of each poncho so they attach together for a roughly 8 foot by 10 foot tarp, the size of tarp the bug tent was designed for. The bug tent has a bathtub floor that goes up about a foot giving a windbreak from all directions while you're laying down asleep. This also gives plenty of ventilation to avoid condensation and allows strong winds to blow through without knocking down the shelter. If it's raining when I have to pack up and leave, I can fold up the bug tent while keeping my gear sheltered with the ponchos and then have myself and a friend put on the ponchos over our packs and leave with all dry gear. Since you should carry a poncho backpacking anyway, and the second person that sleeps in the tent carries the other one, the added pack weight of the tent ends up being a little over 1.5 pounds. Trekking poles are used as tent poles and help you when hiking, ponchos are essential gear anyway, and you're left with 26.5 ounces for the bug tent and 1.5 ounces for 6 titanium tent stakes. Total added weight of tent is 28 ounces for 2 people. This setup gives you no slippery floors, no condensation problems, no bugs, ponchos can be buttoned the other way for emergency bivy sacks, and Multiple setup options (ponchos, bivies, 2 person bivy, sunshade/cook area shelter, bug tent, full tent, ground sheet). The only drawback of my setup is that the seam between the two ponchos has to stay to the side to keep rain from getting in.