So to answer you first question, no Flexi is not the only rip that you can use. It's just a corporate synergy thing. You should be able to use any rip you want. If you did decide to go with Flexi you would not have to design in it. I often design in Composer, Illustrator, Photoshop and Corel. You would just need to save your files in a format that Flexi Production manager can read the safest bet would be .pdf. Flexi Design is capable reading .eps, .ai, .psd, .png, .jepg, .pdf, .tiff and more so if you wanted to create the bulk of the art in another software but put the finishing touches in Flexi you can do that as well.