He's not untouchable and whether he is a good bloke is irrelevant.
What he is, is one of the best keepers in the football league who had numerous top top class performances the last time we were in the Championship. We could well decide to sign another keeper for competition/cover but we certainly don't need one.
I think it's hard to say what we need to sign as most of our players are good enough to do perfectly well in the Championship - the real test is organisation, teamwork and profesionalism. We might need an extra centre back as, apart from Fonte, there must be a question mark over the ability of all the others to do well at that level now (I'm sure Martin will prove to be god enough eventually and Jaidi obviously was at one time, maybe he still is).
I would also like to see us sign another right sided midfielder as Guly is not really a winger and Forte looks more like a front runner to me, but it may be that another player from the development squad will provide an option there.
We don't need big structural adjustments. However, once you hit Championship level there are more players of genuine quality available (ie Genuine top-flight players like Bellamy). One or two "big" signings to add undisputed quality to the side should be all we really need.