First, let me say that the Arcanist appears to be fairly well balanced by the numbers, that the spell preparation mechanic is a nice compromise between the sorcerer and wizard styles, and Intelligence seems like the correct ability score to use. Now, on to some questions and criticisms.
The name "arcanist": isn't this word already frequently used for arcane casters in general? Just a nitpick. Maybe there's not a better name, but if there is, I would probably prefer it.
Mechanical issues: Blood focus is an interesting, but it applies to a lot of class features that weren't written with it in mind. For instance, what if I choose the Arcane bloodline? Can I use Arcane Bond to gain a familiar for rounds/level, or a bonded object? Can I do each, separately, in the same day? Can I do both at the same time by summoning one at a time? Further, some of the features are written with the sorcerer or wizard specifically in mind. The bonded object for Arcane Bloodline specifies that it grants one bonus spell from those known, not one from the spellbook (like a Wizard), but the latter would actually be useful to the arcanist. It seems like more specificity would be useful, or maybe the existing abilities need to be reviewed if something needs to be adjusted about certain kinds of abilities.
Flavor issues: This class consists mostly of numerical bonuses and metamagics. Apart from the bloodlines, which it gets from being half sorcerer, there is nothing new here. I would strongly consider playing a wizard and taking the Eldritch Heritage feats over this class. It also uses slightly complicated bookkeeping to keep from overstepping each alternate class, especially with uses per day. The whole class could be replaced by wizard spells that roughly duplicate some of the desired bloodline powers. A wizard archetype that replaced bonus feats with some sorcerer powers would be simpler. Apart from the happiness of a blood focus (evocation/elemental fire) blaster, I don't see a lot of improvement over existing options. I think overall it needs to either be simpler or more exciting.
In keeping with the arcane theme, why not build arcane bond into the class? Maybe familiars could gain some bloodline powers. Maybe bonded objects could gain some bloodline related bennies.
Since they are masters of the magic in their own blood, what about some kind of feat or class option to blend in a secondary bloodline? If I could have an Infernal familiar with a mixture of Infernal and Elemental Fire powers through my blood focus, that begins to get interesting.
Oops: just saw the specific class subforum. I'll copy this over, ignore.
Locking this thread so we don't have parallel discussion in two threads. :)