Vents may be either wet or dry, and you would need to know which you have for each fixture.

For example, the sink vent may be a wet vent that runs up the wall to the roof, but also has a connection that drains the shower above. Therefore it vents two fixtures, with the lower sink having a wet vent and the shower on the 2nd floor a dry vent . In that case you could not cut the vent line at the sink and use an AAV because the sink vent is also a drain for the shower.

Bruce

Thanks. For clarification, the shower is on the same floor as kitchen and the venting at point of conflict runs over the shower. There is no bathroom or plumbing above only an open loft. The only half bath up is on other side of the home over 30. ft.

Sorry you lost me and without at least some sort of drawing I have no idea of the issues involved BTW where is your plumber in all of this?

A picture or diagram would help a lot to lessen the confusion.

Bruce