Exploring options is good.
I also believe a BUG is extremely preferable to a knife. I carry both, a Kahr PM9 (support ankle) and a Benchmade 5000 (support pocket). I was never trained in knife-fighting, but I have picked up a few tips and self-taught to some extent. I had done the same training method for years, being entirely self-taught with firearms, picking up whatever new good advice I could learn, before ever receiving any formal training. That worked out fine. I learned some at firearms training, but was already in the top 1% of the academy class.
Am I knocking formal training? Not at all. There are only 2 problems I encounter:
Finding a good trainer
Getting into the class through time/driving/money
Good trainers help YOU train. You need to be able to figure stuff out (train) on your own. You shouldn't require an instructor to help you learn things all the time. (That's a crutch.)
That said, only perfect practice makes perfect, so be sure what you're practicing is a sound method. Then determine what the best employment is. Then practice that.
I won't tell anyone I'm a knife fighter (never told anyone I was a gun fighter either), but if I feel it's in my best interest to hit that Auto-axis button and slash/stab a guy, that's exactly what I plan to do. Mostly it just sees tape, boxes, and the occasional rope.
My only practice consists of "air fighting" imaginary perps in my living room, much like how I practice room clearing. (Yes, it looks ridiculous!) I've tried over and under-hand gripping. There are strengths and limitations to each. There's slashing and stabbing, which are obviously different techniques. Nothing will simulate going through a rib cage or slicing a neck, but at least I have some teenage hunting experiences to draw from.
My current partner and shift sergeant is the defensive tactics instructor for our agency. He's great with Tasers, batons, and fighting/grappling, but we both admitted knives were an under-developed skill area for us. I picked up a Cold Steel rubber training knife at Knob Creek, so after finding chalk powder we intend to "play" with that on our mats and see what we can learn...
(OK, mostly I learn.)
Sparring is awesome for learning!