When I was growing up, our family would spend a couple of Sundays every month at my grandmother's house having dinner. She was a first generation German immigrant, and Sauerbraten was one of her specialties. We didn't have it often because it took several days to prepare, so it was more of a special occasion dish.
I still make it once in a while, although I've varied the recipe slightly. My grandmother's recipe (which I assume was handed down to her) called for the addition of white wine to the marinade. Grandma was a teetotaler, though, and never added it, instead using apple juice in place of the wine. I've gone back to using wine in the recipe. In her day, I assume the wine used would've been something like Riesling. Instead I usually use a dry red wine.
Grandma didn't add gingersnaps or cake to her gravy. She just made a roux of flour and butter and added pan drippings, along with some of the marinade to make gravy. With the apple juice, it was sweet enough as is.
You could probably get away with using a smaller piece of meat, although it would probably affect the time in the marinade. My recipe suggests 3-5 days. I would definitely cut it down to 2-3 days, lest you end up with a very vinegary roast.
The other option would be to marinate a larger roast, then cut it up into smaller pieces and freeze. That would give you a few meals.
By the way, the old recipe I have calls for "stew meat." I don't know what that translates to in today's world, but I'm fairly certain my grandmother used bottom round.