Decent viewpoints mate, pretty sure the player you have alluded to is Evans like, which i am very mixed on, think he is a player whose price is at an optimum atm due to a purple patch of form and whose at an age where if he loses a step we could end up bacdk with the same mess at the back come a seasons time - then again i don't think that type of signing would worry Allrdcye as it fits the maximum window he would likely be here anyway, so would become the next mans issue.
as for Gaitan - think he's someone who needs to be playing regularly, but whilst his time at Athletico has been mixed - look at the talent he has to get past in that team? at Benfica he was brilliant and consistently so when played regularly, both in the league and in Europe for them. There also comes a point where having a lot of solid types with little ability to do something different sees you with a pedestrian and predictable team which is easy as hell to stop - which is what we are now and under Koeman for large parts.
De Vrij has had a lot of niggles over the last few years, but when fit is a very good player, again - we aren't gonna get a top end cb (which he is) who doesn't have some issues, the key is to identify the ones worth that sleight gamble on, otherwise again we end up with a 'dependable' but ultimately bog average team. checked his injury history and he's missed 15 games with about 7 separate knocks since knee surgery a season and a half ago, which taken as a whole means he's been available about 80% of the time for Lazio, played 31 games last season, played 22 so far in this, would suggest he is worth the risk.
Tierney you are probably right about, BUT i honestly don't see Celtic turning down a big offer especially if it comes from the type of team willing to give them then a sizeable sell on fee - and the type of team who they can be pretty confident by their history can get massive fees for players like Stones and Lukaku etc. Failing that - Shaw i do like and would, likely be available, and the lad from Bristol seems the last resort for me, could be good, at worst is a lot better than what we have atm.
Turan - again worth the gamble IMO, plus would definitely help with Tosun settling at the club bringing in two of the same nationality etc - and with one eye on him and Gaitan both fitting the past model of Allardyce getting a tune out of a creative once great player whose noit had the best of it the past few seasons etc.
Nzonzi - no brainer to get him, performed well ij this country before,performed very well for the manager, and has only improved from his time in Spain
Honestly don't know much about some of the others being linked lately - like Seri (who looks good in clips etc) and the lad from Hoffenheim - who again looks a very good player from what i can see - and fills the Turk quota nicely as well, same goes for Max who looks and who has the stats that say he could be a very good player, but doubt any of those are realistic shouts