It just depends. And there really are no "ball park" answers since it can vary so widely. Yes, domiciles are one factor. Yes, even new hires sometimes get hired into wide body jobs. Yes, seniority is a factor, as it is for everything at the airlines. And, as someone pointed out, if you're flying cargo versus passengers in a major passenger airline like American, Delta, or United, you may be able to do it faster because the cargo airlines fly much more wide bodies than narrow bodies.
Even more than the above, it depends on the economy and the health of the airlines. Right now, that's not a problem but just a few years ago, the airline industry had some huge challenges to sort out and there was a lot of stagnation in our careers. This is a cyclical industry. It can (and will) happen again. Maybe not soon. But it will happen again. Prepare for that.
My bigger question to you is ... why the hurry to get to the wide body job? It may not be all you think it to be. If flying wide bodies is some personal dream and you're willing to sacrifice all other factors to do it, then it may be possible in short order, but at a cost.
Every airline position comes with its' pro's and con's, depending on your both your OVERALL seniority in the grand scheme of the airline and your RELATIVE seniority in your bid status, the group of pilots who do the same job you do. At every stage, you make a decision to jump to a different pond (bigger equipment, different domicile, Captain upgrade) based on a combination of Quality of Life (QOL) and money. You can be a big fish in little pond, or a little fish in a big pond. Yes, bigger equipment generally pays more per hour. But if you're willing to work a few more hours a month in a narrow body job, you may find you can make up much if not all of the difference, depending on the airline contract. Meanwhile, your QOL will be higher because you'll be relatively more senior in your bid status so you'll have much more control over flying the better trips, getting weekends and holidays off, getting preferred vacations, etc. A lot of senior domestic narrow body FO's stay as FO's long after they can upgrade to Captain because they can hold easy daytime turn trips that pay well and have them home every night.
Meanwhile, most of the junior FO's I know on the wide bodies are on reserve, meaning they are on standby-to-fly with no scheduled trips for the month. They are on the hook to be available more days than a narrow body lineholder. While they may (in hindsight) have many of those days off, they don't know when they'll be needed to work so they can't make firm plans on those days. They may have little or no control over the trips they fly. They may be flying FB or FC (as a backup pilot) who doesn't get any takeoffs or landings, so they go non-current and have to return to the simulator to log landings. I've personally seen pilots lose proficiency flying wide body FO and have some struggles when it came time to upgrade to Captain on a narrow body. And since they are junior in their bid status, pilots who choose to be more selective about bidding that status will continue to come in "on top" of them for a long time, making them perennially junior. Your status in the wide body fleet is based on your system seniority, not how long you've been doing the job. So they move up little or not at all. They may even go backwards in their seniority in their bid status. If there are cutbacks in their bid status, they are the first ones to be displaced to another base or airplane. Always "chasing" the next upgrade as soon as possible can be a more volatile lifestyle. And international trips often do more "back-side-of-the-clock" flying so you may be doing much more all-nighters than you would if you were domestic, if that matters to you. Some guys love them. Some guys hate them. It can take a toll on your body.
Yes, the wide body international flying is more "glamorous" and you get to visit fun locations. But before you set your sights on it, make sure you understand the consequences and what you will be giving up if you do it too quickly.