Your Option To Purchase can be
modified to suit you, the Vendor. Donch listen to agents who tend to say the OTP is always standard or cannot be changed (remember it is draft). You should have asked the lawyer to redraft/negotiate the OTP to ensure that the revised OPT is mutually agreeable to both parties.
And also like some of the other bros in this forum has indicated, have the indemnity form signed by the Purchaser(s).
Maybe your lawyer jumped because he works very slowly, and cannot get all the necessary submissions and/or the bank redemption etc in time
This looks like a lose-lose situation to me.
1. 3 and half weeks to exercise option. (standard is 2 weeks)
2. 6 weeks to do completion. (8 to 10 weeks is common, but 6 weeks still do-able)
3. Renovation works start 2 weeks before completion. (get them to sign the Indemnity form lah)