The comparisons with Guardiola just doesn't hold for me.
Firstly, Giggs has no personality to speak of nor most importantly - intelligence off the pitch - at least any that I can recall.
Next, say Guardiola had started off badly, I don't think it would be such a disaster for Barcelona as it would be for us in the Premier League - because let's face it, it would be easier (not easy) to haul yourself back into the top four there without too much trauma precisely because they don't have at least 6 or so teams that can challenge for those spots as we do here.
In contrast, Giggs would have to keep us in top four, appeasing not only the fans but the money people and the sponsors. Has anyone stopped to think just how much pressure is involved with that?? Giggs has no life experience outside of United - how on earth is he going to cope with all the expectations?
For those reasons, I think Giggs taking over would be a much bigger deal for us, and thereby makes the Guardiola argument redundant in my view.
You cannot be idealistic with these things. In contrast to Man City whose owners have unlimited funds due to oil - United depends on sponsors to bring that cash in. You are asking the club to risk a lot of people's livelihoods and the well-being of the club to continue building on our success, just to realise some romantic notion. That doesn't sound logical to me.
Giggs really needs to go out and show he can achieve like Simeone. If he is good, he will be able to show it anywhere he goes, so why are people afraid to see him go out and try? At least we will know better whether or not he deserves to be hired in the future.