Why dont you register new trade mark, change this slightly and continue? If they have patent only on trademark they got nothing to hold you on technical side of the card (that you in fact developed and that is worth something at least in my mind). Also, trade mark without a commercial basis is worth nothing and you dont have one, yet. I really see no problem for you. Maybe from ethical point of view from ppl your worked with but not from the point of company.
Namely, we registered some patent recently and I found out that ppl are not understanding difference between trade mark and patent. Also, there are two kind of patents and substantive examination patent is the one that you can protect your technical solution fully and that one is tougher to deal with but probalby you (or somebody else) will never be able to get this kind of patent as it is really nothing new in your work. What is valuable is your work itself and trade mark really not problem for you.