i don't have any hands-on experience with any busse [or kin] blades yet so i'm not familiar with their blade thicknesses which imo should be a major factor when considering a small, piggy back companion blade.... you specifically mentioned bushcraft duty and since you've already made your choice to field carry 2 blades [as opposed to three separate crossover duty blades or a 'single do-it-all' one], and have the h/d chopper choice made already, imo you'll want to use a relatively thin blade for the 2nd, small - piggy back - knife choice...
most active bushcrafters go with a convex grind large chopper [or more typically, a quality half-axe - wetterlings or gransfors bruks are popular and among the best] for heavy wood chopping/cutting and a much thinner small blade for all around camp duty such as game dressing, food prep, fire starting/prep, etc... scandi or hollow grind for the small knife... you'll want the small blade to be light as well for extended fatigue-free use....
many hard core bushcrafters tend to ridicule dudes who choose a king size, thick blade as 'rambo wannabes' but that's because they're usually quite proficient with using a small, thin blade for all but the heaviest tasks around camp/fiield, through a lot of long term practice.... to most practicing bushcrafters, just about any blade that's thicker than 1/8" and longer than 4" is an excess.... more often than not, a bushcrafter's combo of choice is a compact axe and a small thin blade combo; often the small knife even without a full hilt [e,g, cheap moras are quite popular], rather than a huge chopper knife/smaller knife combo....
however, an axe is awkward to 'wear' so it's usually relegated to being strapped to a pack or another carry method outside of a person.... therefore, if you like to have both blades strapped and always on you, a large, heavy chopper knife insteadd of an axe is a better choice, as long as it's truly tough and proficient at chopping...
someone mentioned barkie's bravo 1 as a good choice for a second blade/companion... i would respectfully disagree, i own a bravo 1 [in 3v] and although its blade is less than 4.5" it is a hefty one and while an excellent choice for a compact/light single all around bushcraft/field/camp blade, its far less than an ideal one as a small companion to the big blade for all smaller chores...it's a pretty thick convex grind too so not as practical for precise carving, cutting and slicing that food prep sometimes calls for for example....
as far as barkies go, the gunny is thinner and a much better choice than bravo 1 despite both being very similar in size and virtually identical in design/shape... i own a day hiker 2 as far as other bark river knives are concerned , and that's a very nice, sturdy bushcraft blade for just about all lighter duty camp/field chores, including skinning/dressing game, carving/drilling a bow drill, etc., yet tough/thick enough to substitute in some heavier use.... hell, you can easily baton with it as long as the diameter of wood is kept proportional to its blade length....aurora is their another badass knife, around bravo 1's dimensions but thinner blade....
mid and larger beckers are also too thick for small, piggyback choice imo....
bottom line, as long as you can alway ensure of having both blades secure on you and ready to use, i personally would choose the second, smaller one to be no thicker than 1/8", under 5" in length and as light as possible with simultaneously very little compromise in strength dept.... full hilt preferrably and a thinner, more precise grind than a convex for intricate slicing of soft stuff like fruit, veggies, fish, et al.... because you won't need it to perform any heavy duty wood-cutting tasks anyway....
i'd use these criteria as fundamental starting point when chosing a companion, 2nd blade for bushcraft duty, whatever the brand/make of choice.... once ya have the various makes/models narrowed down to this factor then it's personal preference with regards to a particular model...
others might disagree of course, that is simply my opinion,albeit formed after indulging my interest in survival/bushcraft skills and subsequent long time study of various sources pertaining to it... not actual practical experience however....
jerzy...
Anyway , so now I have a Dogfather as my chopper and would like oppinions about what you guys with more Busse and Busse kin experience think is the best smaller knife for bushcraft . 
