I went down this path last year. I've always disliked spinning gear on the whole and far prefer casting gear. I didn't want true BFS per se, but the ability to throw down to a 1/16 head on a light 3" plastic (total weight around 1/8oz). On the upper end a 1/4 oz plus a 3" medium plastic (which I can throw on plenty of other casting gear also). My thinking was that I could eliminate spinning entirely and only carry this rod, then on top of that it would be useful for other light applications to take load off my other baitcasters. Fishing out of a kayak, I carry 5 rods typically and with the specific rod holder setup I have a spinning rod is a pain to fit as I can only put it in 1 of the slots due to the extra size of the handle and reel. So grab a BFS setup and leave the spinning rod home permanently- that was the idea. I went with the KastKing Zephyr (bought used here in BR) and the Phenix ML after a bunch of chats here about what I wanted to do. I figured if I didn't like it then I wasn't out much and if I did then I could probably recoup most of my money on an upgrade should I want one (or keep it as is if I like it that much as lots of guys do).
In practice, the more light stuff I fished last year (primarily neds) on both spinning and BFS (usually in the same trip) the more I see the need for a spinning rod. I still prefer to cast a baitcaster and the thumb control for distance/placement is just too natural to me. For ligher moving baits like a bomber little A I prefer a casting rod. If I'm fishing to targets then the baitcaster is just better for me for that. If I'm fishing a broader area or fishing neds at distance, the spinning rod is just better. With the same bait the spinning rod was outcasting the casting rod despite giving up 4" length. With lighter stuff even moreso. Of course distance isn't the be-all-end-all and the Kastking's braking system isn't the best. But if you want to throw a ned rid 40 yards the spinning rod will just do it more easily. Then on top of that, I found that my mentaility changed fishing a spinning rod and a casting rod, even though both had the same bait and the same line. The spinning rod is a finesse setup. I was treating the casting rod the same as my heavies- pitching into heavier cover than I should, eye crossing hooksets, etc. That doesn't work with 8 lb fluoro leader. That's a function of me and not the rod, but after a year of doing it I never changed my ways.
I'll keep the BFS setup and I might even upgrade it. An aldebaran BFS has been calling my name and Falcon just came out with a new BFS type rod (more like a light casting than true BFS which is fine with me). But I've hesitated on that. You know what I didn't hesitate on? Another spinning rod setup even more geared to neds than what I already had.