I have played guitar for 20 years and I do not use a pick. Assumably, I am the antithesis of SubNetMask - don't bother asking me a Clapton Question...Ha! Anyway, I play mostly traditional fingerstyle music on Dobro, Guitar, Banjo, Lap Steel, etc. Yet, I had the great honor of studying with Jack Cecchini for a bit about ten years ago when I was on a classic guitar kick.
I would tell you this. Essentially, you cannot serve two masters simultaneously. Can you play classical songs on a Martin? Yes. However, it is important to note that the manner in which one approaches the instrument when playing the classic guitar is wholly dissimilar to the approach applied by one interested in playing a Celtic solo on a steel string. It is simply not possible to obtain the delicate touch and tone one needs for the classic guitar on a steel string. Further, there are technical aspects such as the extensive use of rest strokes, Thumb and Hand position, etc. that differ from the techniques employed on a steel string.
So, if you are interested in playing beginner level classic guitar songs, there is no need to make the switch. However, more advanced material will be very difficult to accomplish and will sound terrible on the steel string. Basically, it's about your level of committment to the music.
If you find yourself interested in studying this type of music, go look at www.zavaletas-guitarras.com, and look for the Huipe guitars. They are an incredible value in student instruments and are available in Hauser and Friederich style builds.
Good luck, and good pickin'!
P.S. You can purchase strings with the ball end, however, some frown upon it.