You've asked for comments...so here goes.
I understand the current trend for a warm cabin on cold days. I like the idea, too, and would love to find a solution.
Bad news: Car starter = very bad idea. Internal combustion engines at start-up, possibly the most critical moment, should be monitored for anomolies. ICEs should operate under load, not idle, for the greatest long-term benefit and efficiency. ICE engines, especially diesels, warm up much more quickly when placed under gentle load during the warm-up process. These are facts, not opinions.
Good news: Your VW has a brilliant solution! Right after starting your engine, if you turn your heat to MAX, and turn on the fan, a very strong auxiliary heater (elec. grid...like a hair-dryer) will click on, and in a matter of seconds, you'll have warm air coming from the vents. Leave it on for a few minutes, and the heat is quite intense, and becomes unnecessary as the coolant reaches operating temp and the regular heater takes over.
I'm sure others will weigh in. Hope this helps.