Bone in chicken breast substitute?

The total weight of 8 (average) chicken breasts is about 3 lb, so you could use thighs (many people find them more flavorful) or a whole cut up chicken of that weight.
Also, BTW, if you read the comments on this recipe, some users had problems with the chicken being dry and the marmite too plentiful and thus strong tasting.
If you like the savory-sweet combination of marmite & honey, I would look for UK and Asian recipes that have similar ingredients.
The Guardian newspaper had a well regarded recipe (around 2015). And some blogs located in Singapore had good recipes.