Interesting that two brand new accounts asked a question (on this thread only!) which seemed perfectly suited to Fr8's "why yes we can!" type of answer.
Definitely. The first Activity is the hardest, because the Terminal builder has to implement the OAuth for that particular web service. At that point, it's easy to add dozens of additional Activities. The core team just hasn't made it a priority, focusing instead on the Hub infrastructure and SDK's
We've designed Fr8 to facilitate that. You can run both Fr8 Hubs and Terminals on your own network, and you can connect you local Fr8 Hub to whichever public Fr8 Terminals you want. For example, you might have a local Hub and a local Terminal that's integrated with your proprietary code/systems, but also opt to connect to public Terminals for Salesforce.com and Slack.