I really like where this is going, @jhash. I think having splitOn and delimiter could create some confusion, though. Particularly if someone changes the delimiter to something like ";" and then pastes something with commas. I think a better default for splitOn is null. Then, when the control initializes set splitOn to something based on delimiter. Roughly:

if (!self.options.splitOn) {
   var delimiter_escaped = self.options.delimiter.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');
   self.options.splitOn = new RegExp('\s*' + delimiter_escaped + '+\s*');
}

Also, the $.proxy calls are unnecessary.