Well if you are into Assassins Creed, it is sort of what you are looking for.
Writing your idea on a public forum and forwarding a novel to literary agents are two different things.
Anyway, you don't pitch ideas to developers - you pitch games to publishers. That means you must have some form of product in development before you pitch it to someone. http://www.sloperama.com/advice/lesson11.html.
Sure, you could use words to describe what you want, however that doesn't mean that is what Bethesda wants.
First off, you would most likely be confined to a single city, see Fallout 3, and the size of Skyrim's map.
Then you would have that city, which I'm not saying would probably look pretty great, but that would be only so much of the map. Then their would just be huge swaths of country with things here and there to see, which would probably get boring after a while. Then they would take it as their responsibility to make the game fun and then make the world some type of "amusemant park" full of cool things and dungeons to explore.
Also considering the time the cities could look great, or be really horrid looking as the Industrial Revolution comes full swing through Europe, well Western Europe.
Edit: That could actually be an interesting thing for the game. If starts off early Victorian or even pre-Victorian and most things look nice. Then you end up playing for decades and watch the cities become cesspools of filth. However, that is also not Bethesda's style.
Open world set in Victorian era Europe? GREAT IDEA!
Speaking of Jack the Ripper, there is an FMV game that was based on the Jack the Ripper. It's called Ripper and is set in the future where people mess with computers and Christopher Walkin is unfreakingbelievable. It isn't what you are looking for, clearly.
I really don't think I've seen many games outside of Civil War based games that take place in the 19th century.
You weren't really clear on it being a suggestion. It seemed more like a request for something. I know someone already responded to this better than I could, but games are expensive to make. There's another good reason why suggestions are rarely taken outside of maybe flash game makers. Even then, making games is extremely time consuming, so the hobbyist won't take a suggestion either because the games take so long to make. This isn't always the case, but that is how it is.
Thief is pretty close to your suggestion, though. It's old and stuff, but it does take place in a mix of Medieval and Victorian. It's also first person, but it's a stealth game series with steampunk. I wouldn't mind seeing your game idea become a game, and do hope something similar happens one day.
If Bethesda ever does TES VI: Hammerfell, you may have a chance
At least, that is where I can picture a pirate population (especially around Stros M'Kai).
I'm beginning to wonder if formal game suggestions and "letters to bethesda" are going to be banned on these forums. So many wasted threads...
Skyrim appeals to older audiences less so than the older TES games in the series. The heavily DND influenced RPG numbers game dissuades those that don't wish to think while they play games. Skyrim is much more simplified and requires less thinking. The vast majority of the young audience doesn't have the attention span to get into a complex game.
Games don't start with ideas. Games start with the willingness to make them. First you become a developer, then you experiment with the mechanics, mold a world around it, and create a story to go with it. When you have something solid, you pitch it to a publisher to get funding to continue to work on it (or crowdfund it). But a game always starts with the mechanics. In part, the mechanics actually tell the story better than the dialogue or visuals do.