dns
Nothing wrong about doing your CPL and ATPL exams before commencing training. In fact a lot of integrated courses and Cadets do their theory first and then focus on flying after.
The chances of securing an airline job after a year is impossible at this stage. It's only possible if you're a Cadet and even Cadet programs are being culled. Once the industry does recover (expect 2022/23), priority will go to the hundreds if not thousands of experienced pilots that have been stood down. It will take awhile for the industry to gain movement to the point where the benefits finally trickle down to the hundreds of fresh CPL/IR pilots competing for a spot in the industry.
To keep current, you would have to renew your CPL and Instrument Rating. As long as you renew your ratings I don't think airlines care if you recently finished your training. Either way it's not going to matter as I'd say there will be a backlog of Cadets anyway. I'm not sure on the exact cost for renewals but I'd suspect it's 3-5k every year.
In this time of uncertainty, it's not worth bleeding thousands every year just waiting for the industry to recover. As others have said, wait for more certainty before making any big decisions.