I think they'd have signed Buendia regardless.... He was boxed before the season finished practically.
As for the rest...
Young - Somewhat ageing, will he be cover?
Ings - 29, and for £30m is overpriced, personally I feel that Watkins is just as good a player. Ings has injuries issues in the past too.
Bailey - probably the only one who will come close to Grealish, but will that weight of expectancy hamper him? Will he adapt?
Seen it time, and time again where sides lose their key player and don't replace him (Everton for example), and I just don't think you replace someone of Grealish quality. So Young, Ings and Bailey or Grealish, i'm choosing Grealish.