There's an article on the wiki that may be useful, especially the part about GParted.
http://wiki.maemo.org/Repartitioning_the_flash

It seems that you're leaning towards the 3rd option. Go ahead and give it a go. Anyway, the 2nd best would be the 2nd option (because the others seem like much of a hassle).

I did some partitioning before with the n900, (actually only shrink /MyDocs and grow /home). Thing went well with GParted. According to the wiki, everything should go fine if the partitions are left in the same order and the created partition is the 4th one.