So thoughts on lovingkindness would be a valid thing to consider while watching the breath Josh? That, or as you say, constant adjustment --for relaxation/pleasure/ease?
I was thinking more about thoughts of energy and brightness, or stillness, or different ways of thinking of the breath as a whole (expanding+contracting, moving up, moving down etc.), but lovingkindness and metta might work too, the best advice is to experiment.
Having experimented a lot I now basically do the exact same thing every time I sit for getting into first jhana, I get pleasure by focusing on the perception of breath moving through the bones, along with the sensations of moving energy that seem to exist in the bones corresponding with in and out breathing.
I've had good results with both approaches but I think the combination of a single anapana spot (or even one that shifts around a fair bit during the sit) and whole body awareness (sometimes just "whole body tingling" other times whole body moving/changing with the breath) seems to work best for me. It seems to give the mind more to do, so better chance of not getting distracted.
I think the two approaches give different results. If you are focusing spatially, that means you are likely causing some distortion. This distortion can cause a type of tingly pleasure, I would suggest staying away from tingly stuff and trying to find a smoother pleasure. What I did for a while was to get the tingly pleasure, then try and tranquilize and widen awareness and move towards the smoother pleasure, or even move through the tingly-type jhanas up till the 4th and then try to widen and smoothify from there. So I think it is definitely valuable to work on both types.
When I concentrate now though, I stay with the widened, smoother type of jhana because for one thing it is much more pleasant, and for another it allows you to see the attention waves movement more clearly which is useful. I think the smoother type is a bit more difficult though, so in the end all I can say is experiment with all your options.