Arcane Casters, spells known (p110). This paragraph says how many spells an arcane caster starts with, but not when new ones are learnt. I assume one spell per spellcasting rank (as per spellbound), but I can't find it mentioned in this section.
This is intentional as it's going to vary by setting. One setting might have characters learning spells as soon as the character is exposed to them (reads a scroll, takes hold of a stone of power, absorbs the essence of a murdered sorcerer, whatever), while another might require research and/or a burning in period for each spell learned. This is one of those things I hope to get an S&P article out there about. (If anyone's game to write it, drop me a line.)
Ranged combat in melee: From what I can see there are no-longer any penalties to taking a bow into a fist-fight. Is this the new direction or have I missed something?
Those penalties will probably return in 10kB. We didn't see a need for them here.
Truly Massive feat: Should this feat increase the character's maximum wounds?
Probably. I'll flag it.
Character size: Does unarmed damage increase with size like weapons and natural attacks?
At present, no. I doubt this is a rule we'll implement in Mastercraft. It's too dense mechanically and has too many ripple effects through the system. Might make for a good optional or house rule, though.