I was thinking both chassis & cab size. Some of those Marshall heads are crazy big IMHO, and the Bluesbreaker combo is similarly large.
I have a JTM45 pre-built chassis in the post as I write this, so I will try and fit it into a smaller cab/combo. When, I originally wrote this I was mainly thinking of squeezing it into a 1x12 combo. And, I am still thinking about this, but I keep changing my mind. The flexibility & cool look of a head cab is very tempting too.
At this rate, I will need a combo & a head