Hello!
So I really want to make a Dhampir, Bladeblind/hexcraft Magus. Wielding a katana that is strength based. How viable is this. I'm not looking for optimization but I always don't want to gimp my character. Looking for advice on how to make this work.
Cheer!
Totally viable, should be no problem (am currently playing that same archetype combo). The katana isn't much of a benefit and will cost a feat, but if it's wanted for flavor Strength magus is less feat intensive anyway. If there's a feat that particularly appeals to you at first level you could wait until third to pick up EWP proficiency and use a scimitar until then.
The obvious choice is to pick the Jiang-Shi dhampir heritage.
Also I keep thinking that you're a kensai because of the katana, writing advice for that and having to delete it.
Make sure to cast Shield before combat, use Spell Combat with Brand when you don't want to use a spell slot. Blindness/Deafness is awesome. Sleep and Flight are great hex choices.
Also check out the kensai archetype (which would net you katana proficiency for free). There's a dedicated guide specifically for this archetype, though Galain's guide is already pretty comprehensive and covers things fairly well (to include the archetype in question).
You could do it, though what one level of samurai would offer you is arguably limited value: the potency of both challenge and mount are dependent on your class level. (I'd be tempted to take Order of the Flame on such a character, just so I could get more millage out of the challenge ability.) On the flipside, though, you could use that as a springboard to early access to other feats; power attack at 1st level is a possibility now (since you're starting with +1 base attack). And maybe having access to the resolve ability could save your butt at a later date - who knows.
You could also just treat the katana as a two-handed weapon and not use spellbattle until you actually get proficiency. (If 3rd level is too long a wait, retrain your 1st level feat to exotic weapon proficiency when you hit 2nd level.)