I hate to say this, but "if it ain't broke, don't fix it". I know about FPE breakers, but the fact is, they are a problem that we have to live with. It all comes down to the consumer. Scott, educate the customer as best that you possibly can, and if they don't listen, you've done all that you can.
Put a clothes pin on your nose, blinders on your eyes, or whatever it takes to get the job done.
Whatever you do, don't over load any circuits. Don't do it, don't do it, don't do it!
Then, in writing (get them to sign it), show the customer exactly where, and what size circuits you added to the panel. Why? Murphy's Law tells me that the day you walk off the outstanding remodel job you've done, they start having problems with the panel unrelated to anything you've done. Then, they suddenly have a hard time paying you for your work.
If there is one thing that I hate worse that an FPE breaker, it's not getting paid [Linked Image]!

Regards,
Doc

The Watt Doctor
Altura Cogen
Channelview, TX