I mostly agree with this, but would add my own thoughts:

If you were an investment banker or a Big 4 firm, and I came to you as a start up seeking VC you would prepare my presentation and projections. You have been down this road before. You take my info and put it in a presentation that you know from experience will be well received by those you present it to.
You have gained experience by doing the same thing last year.
If you come out of college and do this for a living, I believe it's an accurate statement to say that you won't reinvent the wheel with every client that comes to you.

My clients expect me to be effective and efficient. I certainly don't re-do financial statements from scratch each year. Or if I have a client A in industry X and I pick up new client B in same industry, I certainly would use, to the extent practical, statement formats, etc of client A and make necessary changes.
You can change the names and numbers to give it a little difference, but I see nothing unethical in what you propose doing.

my $.02