RE: [Rails] Re: is it safe to use rails engine?

I like em

But im interested in what all the concern is about their use

DHH isn’t (or wasn’t?) a big fan of engines:

Also the core team doesn’t seem to worry much about breaking them since they use non-public Rails API methods.

To the OP I think the 3rd option is your best bet. The functionality you describe is easily categorized into separate web applications.