Pereira is the most logical bet I would say, as the others have long contracts, and I don't think we would spend a lot on those positions right now.
The plan to move Roberto to midfield is great though - and I don't really care who we find as a backup there. But apparently Palencia isn't good enough yet?
I doubt Palencia will ever be good enough. He'll turn 22 on Friday and his time is running up. He's a very likeable and easy to root for kid and I would give him a preseason with the first team to impress EV but I just don't think he has what it takes to succed at Barca. You never know though and maybe he'll prove me wrong.
I don't think his market value is high so we probably wouldn't get much by selling him and he won't improve staying in Segunda for another season so I think loan or sell with buy back option would be the best for his career. If he'll prove himself good in smaller club then we can take him back or maybe he'll just improve his value and we'll get more if we decide to sell in 2019. And at the same time we would open a starting spot in Barça B for younger Morer and especially Morey (who I think is more talented) to prove themselves.
About Pereira: it's true his contract is expiring next year so from that standpoint he'd probably be easier to get but we're still talking about negotiating with Porto who usually sells their players well above their market value. We've made a great deal with Gladbach for MATS a few years ago so I guess we're still in good relationships with them and maybe they would sell us Elvedi for more "friendly" price. And about Henrichs I wouldn't mind another German here. You can't really get wrong with them, can you?
But as said above I haven't followed any of the players mentioned above enough to know who of them has the best potential and/or who would fit us the best.
Depend on how EV rate Cucu and Miranda, but I doubt it, we have been linked for LB for a year now so if rumors that we are going after a RB it feels that we have more faith in him. May be are thinking about making him a back up LB and back up CB at same time?
There were rumours a few weeks ago we've decided against buying LB because we have high hopes for Miranda who could be promoted in the next 2 years or so. Before that I would really like Cucu to get a chance. If we sell Digne (nothing personal against him because I like him) and buy a versatile fullback who could cover both RB/LB and possibly CB too (but mainly as emergency 5th CB option in case of injuries/suspensions and nothing more) then I think chances for Cucu to get more playing time would improve. He wouldn't have to be promoted (unless he'd earn promotion with impressing EV in preseason) but could be called up for Copa games or when Alba would be rested. Having another versatile player would also add more flexibility to the roster which could be important because we know EV prefers smaller squads.
Then we'd have Alba and Semedo (he has to earn that first though) as starters with that versatile new FB to cover for both with Roberto possibly also playing RB occasionally and Cucu being called up when needed. But it will probably be tough to find a player who could play both RB and LB good enough and I don't know if any of the mentioned players could do that so maybe it's the best to stick with what we have at RB/LB for another season (and then re-evaluate things) and use money to improve other positions this summer. We'll invest 130M in Arthur and Griezmann so I doubt there will be much left anyway unless we'll suddenly learn how to sell players. Getting 35M for Rafinha (so we'd basically exchange him for Arthur from financial standpoint) would be a good start. But can we get another 50-60M for selling other rejects? We'll see.