I am going to go out of place here and recommend finding a good coach if your budget allows it. I travel a great deal for work and have a highly variable schedule. Sometimes it changes on a moments notice. I found a coach who is also an airline pilot, and as such he understands travel and it's limitations. I have been working with him now two months and am extremely pleased with my
progress. I happen to train with power, but many coaches will do hr and perceived exertion training. He is able to tailor a plan to my schedule, and readjust it if I miss days,or want to work out a day he had for a rest.

We communicate through email and I post all my rides to training peaks for his analysis.

It really keeps me going knowing his going to nosing he is going to be on my ass if I slack off, and he keeps upping the bar on me just when I get comfortable. I am positive I would not have come this far in this time without him.

Maybe you can find one that meets your needs too.