I think replacing Blaze with Amy as the girl closest to Sonic would be stupid. Amy is second character most important to Sonic besides Tails. If he wanted to get rid of her, he’d wouldn’t put up her screwups to this extent. Also, even if Amy didn’t exist, Blaze being Sonic’s love interest still wouldn’t happen. He’s not Urkel, he doesn’t have the patience to coax her into admitting her feelings.
For starters, when was it stated that Blaze would replace Amy?
Second, when has Amy completely screwed up? She got captured once in SA1 and was more than able to handle herself whist escaping thanks to Gamma, and another time in SA2 where he was holding BOTH Tails and Amy hostage. In the next game, (Heroes) she was on her own team alongside Big and Cream & Cheese to save Cheese’s friend.
Third, if Blaze was to be in Amy’s place, what’s to say Sonic wouldn’t have the patience to have Blaze open up to Sonic, that’s what he did in Sonic Rush to have Blaze accept help from others.
Sonic isn’t some impatient asshole when it comes to helping his friends.