i think what you want to achieve is fiddle breaks between vocal phrases. so to achive what you want you might have to mute the rhythm fiddle playing chops where you want the fiddle breaks to avoid a clash and use multiriffs of a solo fiddle in the bars betweeen vocals.

depends how it sounds you might want to leave the rhtyhm fiddle playing and just add the breaks as a separate instrument - i've seen lots of old country bands with two fiddlers and the clip here show that you can never have too many.....

https://www.youtube.com/watch?v=eHJPHjb6WN4