I am in a similar position - working home office for a larger company. I only see the headquarters 3 - 4 times a year for a few days.
I have introduced gradual changes too - changing my avatars on chat apps and webex to a girl avatar and snuck my female name into my email signature as "middle initial". Did get a few questions about it but it did go mostly unnoticed. One person knows so far.
Where it does get more interesting is that I have one specific customer assigned to me and I am there at least once a month. There I also have one person who pretty much noticed last October and she filled me in about a good portion of gossip going on about my latest changes in appearance (longer hair, ear rings and while still discrete full female outfits). I also have a four week assignment with them next February and given my HRT progress I will not be able to hide it any more. Next time I am up there I will have to break the news to my direct contact and come up with a plan to let the rest of the group know. Very liberal place, so I have little worries. Only catch is that if I break the news to them I will have to also fill in a larger group at my company.
I like Devlin's idea of gradual changes to ease people into your changes.
At the same time you should check your HR policies on discrimination. Most large companies have explicit LGBT policies or even groups. At a minimum they have non-discrimination clauses.
At some point you will face the question to tell HR and your supervisor. Something I am trying to push out as long as possible. HR I don't care about, my supervisor is somewhat rude and some of the folks in my team will have a hard time to digest this. Usually an HR department should be attempting to help in the entire coming out process and there have been several great examples discussed here.
Once you make any changes in such a system you should be prepared to get a few questions and potentially a call from HR.
Now I'll check if our system has that option
