There's still a lot of money in the Thomas Cook name, despite the bankruptcy.
The biggest challenge with starting a new airline is getting people to remember your name. That's not an issue with the Thomas Cook branding - everyone will recognise it and remember it fairly quickly. Thats going to drastically cut your marketing budget. Most peoples memories are short, by next year they'll have forgot that they went bust, and most will be happy to book with them.
Let's not forget that Thomas Cook raised £900m in investment from their Chinese owners before they went bankrupt - clearly they saw the potential in the investment even in the state the business was in back then - a new startup can cherry pick the best parts of the business, while ditching the loss making parts with no cost.
For clarity, my suggestion is to create two separate businesses. 1) Thomas Cook Airlines. This would exist as an airline only operation, following a model similar to Jet2. Offer flight only options, but also offer package deals including a hotel. Partner with travel agencies to also offer these packages through the stores.
2) An independent travel agency with high street stores. I dont believe the high street travel market is quite dead yet. There are a lot of people who just dont trust buying online (the older generation especially), plus lots of people that just arent clued up on airlines and travel, and need the guidance. These people want to be able to walk in to a store, see the special offers and sit down and chat with an adviser. Thomas Cook had something like 500 stores, and had recently decided to close just 21 of them - we can therefore assume that the rest were reasonably profitable then. 500 might be overkill, but there's definitely room for stores in some of the larger towns.
Normally I would say there was no space in the UK/European market for a new startup, but I think right now there is indeed a vacuum that is yet to be filled. A new entrant getting in quickly has an opportunity to take up some of the spare capacity that has been left in the market. If I had the money.. I'd certainly consider it.