You mean you wanted to be able to insert records into the subscriber and have them appear on the publisher as well? If so, you have a few choices:
1) Obviously merge is the most common way to do this.
2) Transactional with immediately updating/queued updating subscribers. Still retains the transactional model but lets subscribers make changes.
3) Roll your own. Do the inserts on the subscriber, then you have to go back and do the inserts on the publisher AND block them from replicating back to the subscriber via a filter - otherwise you'll get a primarykey violation. Updates...oh, you'll have fun implementing that!
1 & 2 are both good choices for your situation. I'd suggest experimenting with both before deciding.