We'll add the thief as the 3rd player as a compromise! 
Why the thief? 
In regards to the cinemas, those would take a lot of work. Besides voice acting, we'd need to translate it, rip the gfx, probably need to recolor them, & add more frames of animation. But what I think would be the greatest hurdle, is the fact that the original PCE Golden Axe relies on it being only 1 player. In it, whichever character you choose, has specific cinemas for that character at the beginning & end. With this being 2 player, we'd have to somehow re-write the cinemas & combine them so that they match up for multi-players.
That does sound like it'd be a huge amount of work, yeah. I don't think anyone would expect all that... it would be very cool if done, but doing all that would surely take a lot of time...
I figure having the thief as a 3rd player, is the most likely way of having 3 players do to his size. He'd still be 1 sprite extra onscreen, same as Ax Battler & Tyris(I think Gilius will take up 2 sprites for him & the axe). I'm sure it still wouldn't work, or if it did, there'd be flicker/slowdown, so maybe as a cheat.
As for licensing, yeah, that could be a real problem. I know when Xseed was brining Ys 1-3 for PSP over, they were trying to include the PCE versions of the music(& possibly others) but there were quite a few hurdles. You have Hudson whose now owned by Konami, you got Ryo Yonemistu who did the redbook, the musicians for the chiptunes, Falcom & JDK(not sure if they're 1 or 2 legal entities), & the original composers(such as Yuzo Koshiro). All or most of these entities being involved made it impossible, or atleast, stupidly expensive.
For Golden Axe, you got Sega, musicians for the arcade Golden Axe, Renovations musicians, & Telenet whose properties are MOSTLY owned by Sunsoft(but not all). So, for all I know, the music of this version could have ties to Wolfteam, & I believe they're part of Bandai/Namco. Most or all of them could be involved. :/
