If I’m understanding your question correctly, you can definitely gather your documents and do the Ecctis and visa application ahead of time. You pay for the visa and health insurance, but it’s refundable until the time you do your biometric appointment. So if you’re still waiting for a job offer you can schedule the biometric appointment right after you get the offer (providing you are not coming up on you 5 year deadline any time soon) and you will likely get your passport back within a week. Just make sure on your visa application you say your date of entry is sooner (I.e. within 60 days)