As I was just saying, I think the proposal needs further consideration.?

>>As的用法 正確嗎 ==.>正確
原句出自Cambridge Dictionary (http://dictionary.cambridge.org/dictionary/english/as)

>>As 這裡是一個conjunction吧? ==>是的
>>as 能當連接詞 嗎? 當然可以
參閱 AS as a conjunction (http://dictionary.cambridge.org/grammar/british-grammar/as-and-as-expressions/as)


As I was just saying, I think the proposal needs further consideration.
正如我剛剛所說，我認為此一提案需進一步斟酌考量
as 在句中的意思，"in the way that"，
例句:
As the forecast predicted, the weather was dreadful for the whole of the weekend.
She arrived early, as I expected.

此一as 的用法多使用於口語，
SPOKEN used for mentioning that something is already known or has already been talked about
As I was saying, we expect next year to be a good year.
As everyone knows, the farming industry is in serious difficulties.
http://www.macmillandictionary.com/dictionary/british/as_1

參閱:
https://english.stackexchange.com/questions/56618/what-is-the-deeper-meaning-of-the-phrase-as-i-was-just-saying-to-x

as置於句首當連接詞帶出修飾主句述部的修飾語，通常提供原因或理由，如：
As it was getting dark, we soon turned back.
As you are sorry, I'll forgive you.
但因as的語意不明確，美語會用because或since代替。
p.72 《新世紀英漢辭典》as當連接詞用解釋5

你的句子內容可能有問題：因為 I think（現在的想法）和 I was saying（以前的說法）這兩件事並不能構成類似上面兩句的因果關係（你句子的動詞時序不符邏輯，應該是先有想法，才有說法）。

此外，請參考下面的例句：
You can't have one without the other, as the song says.
這是用來引用他處的話。
see p.1379 Collins Cobuild English Dictionary for Advanced Learners

PS:發現Cambridge Advanced Learner's Dictionary p.61出現你的句子當as做為conjuction用法的例句。as = in the same way。所以該句是正確的用法。

as--adv.prep.
"as for "used when starting to talk about a new subject connected with what came after,when speak of, concerning about;
eg:-As for it, I think the proposal needs further consideration.
As used as conjunction used in comparisons:-eg:-
The proposal, as you know, is considering.
As I said, I'm considering the proposal.
As there's time, the proposal needs consideration.
The proposal being pending, as I was considering the proposal further.

邏輯有無錯誤，將句子重整即可，I think the proposal needs further consideration as I was just saying.as此處當連接詞所引導副詞子句，修飾其前主要子句，而as 引導子句在前且用進行式，表更強調我所說的，意思為就如我已在之前說過，我認爲此項建議案仍需再考慮