It's not that much time. It's been somewhere from half a year to a year, right? It definitely cannot be more than a year because there hasn't been a new class. And unfortunately, there's no way Sakuno can be good in less than a year, especially since she doesn't play religiously like the rest of the PoT boys. Not to mention that they all have been playing for years.
As for Echizen's situation being simliar to his father's, I don't think he wants to be like his father. ^.^'
If Ryoma + Sakuno get together, the perfect time would be now b/c Echizen forgot his memories.
Sakuno can kiss him and he regains memory? Well its unlikely b/c Echizen doesn't show strong feelings for her (maybe secretly? we need a flash back, flash backs can explain/make anything possible, a flash back of Echizen looking at Sakuno pictures on wall of his room?)
Actually the best time would of been before Echizen lost his memories, b/c then Sakuno would of already had a strong emotional connection. ^well like I said, we just need a flashback.
Echizen regains abilities by all those guys going to play a match right now in latest chapter. Sakuno helps Echizen remember... hmm... im not sure. Maybe Sakuno helps Echizen remember and Echizen falls in love.
Ahh.... another way is Echizen not remembering (even w/ help of those guys) plays Yukimura, Yukimura shows super strong shiny attack and Echizen is blasted into the stands or into the wall or something w/ a bleeding concusion/head and Sakuno rushes to him (like in the first episode) and brings her hanky.