Hi, Genelle,
I believe you may be right. I have recently read some commentary on that passage of the Didache that suggests that, as Gentiles were initially coming into Torah they would ease into it rather than trying to do all 613 commandments the first day. While they were learning and "easing into it" then "do what you are able" was more of an encouragement to keep going.
I like your perspective on that phrase even better and fits with Paul's exhortation from Romans: "shall we go on sinning that grace may abound? By no means!" (Romans 6:1-2)
Thanks for sharing! 
