Only reasons I can think of is mostly that we will have to get the new coin listed on an exchange again, also I told the Bittrex exchange operators we were planning on upgrading Swing, so they might get grumpy if we decide to go with a swap instead. Also it would take some time to build everything and prepare for the swap.

However, if we think a swap is the way to go I'm fine with that choice.

(I suppose we also have the option to upgrade Swing, and coin-swap to something new as well. Give holders the choice to stay or swap.)