I am looking for a convertible jacket with a 7-in-1 system. I can't find any. Do they exist?
Several companies offer convertible jackets. In fact, they’re pretty popular, althouth the most common combination is 3 in 1, not 7 in 1. A good example is Marmot's Frontside Component Jacket ($300), which has an outer shell made with Marmot’s waterproof-breathable MemBrain fabric and an inner removable fleece jacket. When it's cool and dry, wear the inner jacket. When it's cool and damp, wear the outer. When it's cold—and windy or damp—wear both. The Frontside works best for skiing, but it would work in nearly any outdoor situation. And it looks pretty good.
To my knowledge, no one is making a 7 in 1, which would mean a jacket with a zip-out liner and zip-off sleeves. To be honest, adding a bunch of zippers makes a jacket expensive to manufacture, heavy, and uncomfortable. And most people have collection of shells, fleece jackets, and down sweaters, and they mix and match depending on the conditions. But if the Marmot doesn't strike your fancy, check out these options from the North Face and Pearl Izumi.
The North Face's Headwall Triclimate Jacket ($260) has a waterproof-breathable outer shell made from the company's popular HyVent fabric. The shell is pared with a quilted, synthetic-fill insulated liner that zips in and out easily. It has more of a tech look than the Marmot, and with a goggle pocket and powder skirt, it's designed specifically for skiing.
The other way garment makers go convertible is to offer zip-off sleeves, which are popular with cyclists and runners. A great example is Pearl Izumi’s Elite Thermal Convertible Jacket ($160). It’s a warm, weather-repellent softshell with zip-off sleeves. It also comes with reflective panels, back pockets, a yellow so bright it'll make your eyeballs hurt—perfect for riding.