「…ならできそう」は次のように言えます。
ーI think I could do ...
ーI think I might be able to manage ...
ーI think I could handle ...
例：
I can't do A, but I think I might be able to manage B.
「Aはできないけど、Bならできそう」
I don't think A is a possibility, but I think I could handle B.
「Aはできなさそうだけど、Bならできそう」
ご参考まで！
カナダ 
