I think going 10 PA/MA for Male/Female (respectively) Samurais would be okay. Male samurais really need some extra PA IMO. They are semi-lackluster damage dealers unless you make them berserk and PA stacked which can do huge numbers but gives the unit really only one purpose at that point. I think seeing a few more skills using a PA as opposed to the MA formula also will see some more use out of male samurais with the slightly buffed PA stat. Poles are a great addition but they really do boost the damage output significantly. I think spears would be ok, but obviously whatever weapon class we go with there will be kinks to work out. Samurai as is, is a fine class. Not necessarily the best SCC class, but for sure a great class to have on any team. I think adding a new weapon option and maybe giving them different PA/MA (or maybe give them 9 speed? Not sure how we would decide on adjusting the PA/MA if they do see a speed increase but, Samurais really do struggle to be even a semi-speedy unit reaching even 10(+) speed, and I don't think 9 base SP would be too OP).
Remember, a lot of little things add up. I would object to bumping Samurai base speed up to 9. Implementing the katana and PA changes and boosting the speed means we're letting the Samurai hit for a ton, and more often as well. Jobs with 9 base speed are plenty strong and are used at a pretty high rate. 7/20 jobs have 9+ base speed, but these jobs are represented more in strong teams, based on the top 8 of S3 and S4. In S3, two-thirds of the units (22/32) were a job with 9+ base speed. In S4, half (16/32) of the units in top 8 had a job with 9+ base speed.
Let's also remember what Gaignun said a little while ago - just because an item isn't being used, doesn't necessarily mean it's bad. Shieldrender looks like a totally reasonable option. Same with Platinum Sword. In fact, Platinum Sword is prob your best bet for getting OHKOs off a melee attack right now.
I think perhaps looking at items/abilities that weren't used in the two most recent tournaments would give us a better idea of which what's generally perceived as "bad."