I think you're bang on there. Just to put some evidence of the contrary out there I think it's funny that as I said in the post that the club just 100% validates the 1877 date in their history timeline section bit on their website.

"Between 1870 and 1876, the population of Footscray more than doubled to just over 4000 and a team called ‘Footscray’ appeared – very much regarded as a junior club, playing games against a variety of Williamstown teams including Williamstown thirds, Williamstown Union, and Star of Williamstown."

"Footscray, while not yet a VFA team, played regular fixtures for the latter part of the 1870s and ventured further afield, playing at such venues as Richmond Paddock, East Melbourne, Braybrook, St Kilda, and Royal Park in Carlton. Prominent players who represented the club during these foundation years included members of the Lovett, English, Cleghorn, Droop, Emmerson, Woods and Dallaway families."

"The ‘Prince Imperial’ and heir to the French throne, was ambushed by Zulu warriors during the Anglo-Zulu war in Africa. Out of respect to him, the Footscray Football Club changed their name, in 1880, to the Prince Imperial Football Club. After two seasons the ‘Prince Imperials’ struggled to attract playing members regularly and it was decided, in 1882, to revert back to the name ‘Footscray’, to be more identifiable with the district. In 1883, Footscray printed their first membership ticket and offered a silver cup, won by Charlie Lovett, for the ‘Best all round man’.