adj+though/as+主语+谓语+主句

Though his eyes are big, he can’t see anything.

Big though his eyes are, he can’t see anything.

【Though the advantages （that owning a business enjoys/ leads to /result in） are considerable/wonderful/numerous, they can not compete with the benefits （that working for others brings about/ causes）, when/ if （responsibility） is taken into consideration /deliberation /account.】

Considerable/wonderful/numerous though the advantages that owning a business enjoys/ leads to /results in are, they can not compete with the benefits that working for others brings about/ causes, when/ if responsibility is taken into consideration /deliberation/ account.

Considerable though the advantages that 。。。 they cannot compete with。。。     

though引导的从句，可用倒装语序，即把从句中的表语或状语放到though之前
如果我们还原句子,那么就可以变成:though the considerable advantages (they have)
至于为什么省略they have 相信楼主已经看出来了,后面主句中的主语也是they.
所以为了重复往往把相同的主语省略.
还原到最原始,最罗嗦的句型就是: Though they have the considerable advantages,they cannot compete with....