Traffic analysis is still possible under this scenario. It's only marginally harder.
How would your magic traffic generator work? Randomly send a packet every minute? Not good enough, it'd be very easy to detect increased activity, which would be correlated to actual usage of the Tor network.
The best you could do is create some kind of Tor gateway that buffers packets. This gateway would always send n packets / minute through Tor in some programmatic pattern isolated from any packet input. If n real packets aren't available, send fake packets in their place. This is further complicated by length analysis; you would need some way to limit the length of real outgoing packets (probably via MTU) and their data so length is indistinguishable from the fakes.
You should also avoid any sort of wireless connection to this gateway, as snoopers could detect this traffic from outside your residence and again break this scheme. And the whole scheme still falls apart if your adversary is willing / capable of entering your residence. Needless to say, many nation-state level adversaries are completely comfortable doing this.
> If n real packets aren't available, send fake packets in their place.
That's what I had in mind, but with a smarter gateway, that analyses your traffic and uses a Markov chain to time bogus packets when you're AFK, statistically similar to what you produce. Better still drown your real traffic in a larger stream of bogus packets.
Sending packets like clockwork is a good way to raise flags at the ISP level (beside using Tor).
The remote proxy should probably be a Tor service, like Silk road was.
Or you could just run a middleman node. Then dummy traffic prevents this sort of easy correlation attack. (Actually, I'm not sure Tor does generate any dummy traffic these days. I suppose you could generate your own.)
You would then create a script on a local machine (say, a Raspberry Pi) that simulates traffic to the proxy while you're not active.