It's a bit difficult to find, but some large companies run small "skunkworks" research teams largely independent of the main operations. This gives you the gene

It's a bit difficult to find, but some large companies run small "skunkworks" research teams largely independent of the main operations. This gives you the general working style of a startup (unusual latitude, variety of work, small and unbureaucratic teams) with the funding and job security of working for a larger company - with some caveats, I imagine. I wouldn't put too much emphasis on 'older colleagues' - it's good to have a range of ages on a team for the different attitudes that they bring. As long as everyone respects one another, it's an asset, not a problem.