I agree that Szczesny* has been promising, but he didn't play a full season of matches, or even a half season. So assuming we allowed the transfer window to pass us by without making a GK purchase and his inexperience causes poor performances (Probably won't happen, but knowing our luck with Goalkeepers, a feasible occurence), then we'd have the issue of needing a Goalkeeper. Although now with Szczesny looking good I wouldn't put this as our top necessity, but if the opportunity allowed for us to buy Manuel Neuer or Hugo Lloris for example, I'd like the club to make the signing.
Ramsey, Wilshere and Song I agree with. Diaby had a decent stint a while back but seems to have gone back to his old, poor performing self IMO. Denilson I have no time for, I personally think he's garbage. Therefore I think we do need a quality player in this area, though who we should go for I can't say. I know nothing of player's availability.
RVP, as you've stated, gets injured too often. Bendtner and Chamakh are not of similar quality to him, nor will Vela be next season, though I do have high hopes for the latter. Another class striker would be a good signing, finishing our chances is one of Arsenal's biggest issues, especially when Van Persie is out.