I suspect a very small core number of staff will be retained - just enough to be able to train other employees
10 years ago, I think it was a case of signing up Easyjet, and then hiring employees to make this operationally possible
Any airline wanting to open multiple routes at Southend will want about 6 months between announcing routes and a first flight. SEN will know during negotiations with an airline if it seems likely or not. That gives at least 6 months to hire people and get them trained up
If an airline wants to open a base at SEN in the next couple of years... there will plenty of issues to resolve but the lack of baggage handlers on site is unlikely to be a major problem