Simple solution, write the word zero on the receipt and calculate the tip in your head and tip in cash, if the server is great, I am usually generous. If they are piss poor, well, they get a tip in kind.
It's funny seeing the reaction of the eager ones to grab the signed receipt before I have had a chance to hand them their tip. The really good servers never miss a beat, the crappy ones become evident. I think it's more rewarding and respectful to hand the server their tip, it let's them know how they did, it also keeps the restaurant out of the loop. A friend's daughter said that the restaurant took a small percentage of all electronic tips, above what the CC fees were.
That large party nonsense can be overrode, I tell them up front I will not be held hostage by the large party charge, if it's an issue, I will find another place to eat or you can break the party up into two or three tables.