I have used my BK9 for chopping and I found 20" Tramonita machete is a better chopper they are about the same weight.
Cant help but feel a machete is really what he needs... maybe something like a 14inch bolo, either that or an brush axe(I realize he doesnt want to use an axe alone).
I love BK knives... I love 1095 "CroVan", but my BK9 is completely USELESS... its to big or to thick or to heavy... or not long enough...
Machetes are made for chopping, they do it well and they are in general lighter then "chopping knives" which they out perform.
Ok mini rant about "survival" knives...

As a tool to replace a knife and a machete... Bk9 yep its awesome... thing is... I would much rather have a machete and a Mora which is very little extra weight.. giving me tools that are much more suited to specific tasks and which cover everything the BK can do... except maybe prybar(if someone says battoning wood I will point out you SHOULD actually use wood wedges to do that and only a knife to make the wedge and wood wedges use less energy and split wood quicker and if you harden them in a fire they last multiple splitting sessions too) Cutting notches in wood to make slots for interlocking pieces for a shelter etc... Tramonita can handle that easily.
Its just my opinion but many survival knives are designed around the "ONE" tool idea... and I believe this idea is a fallacy...
I cannot think of any situation where I would be left with a single tool, and if some situation did eventuate that it would as if by magic manage to leave me with my "ONE tool" knife.
While having only one tool means should it break you are totally screwed... if a mora breaks.. I have a machete, if a machete breaks... I have Mora... if a BK9 breaks... and lets face it they can you are left trying to salvage it and you may be in a situation where you need a functional cutting tool and dont have time to try to make a broken blade into a semi useable knife. Also you can always just plain loose things... having more then one type of tool is always helpful. Machetes take far more impact energy.. and do so without breaking then a chopper... longer blade means the tip is moving faster... and suffers greater impact... how often has anyone heard of a good Machete breaking? Its my opinion thick survival knives are a joke.. and product produced from 80s action movies rather then real need and effectiveness.
Ok mini rant over
