What could be the most ambitious but scientifically achievable mission to Europa within the next 50yrs?

The Europa Clipper is on track to reach Europa by 2030. If the probe found tantalising potential life signatures and a decision was made to follow it up with a much more ambitious mission, possibly even a submarine, what could be the most advanced mission we could deliver using our engineering capabilities within the next 50yrs.

I specify 50yrs as those findings would be something many of us would still live to witness. So, within our engineering capabilities, what kind of device could be built and how, and what could we discover?

Let's say we had a large nuclear melt sub. Any ice melted will freeze back almost instantly. What if the sub dropped off a series of relay beacons during its descent. Rather than needing a powerful signal to penetrate 15km of ice, it would just need enough to penetrate up to through a series of beacons up to a lander. That way we would have a virtual signal tether between a sub-surface probe, surface lander to an orbiter.

That way you could avoid needing a 'hot' cable. These are the kinds of engineering challenges I wanted to see address. Clever ideas to overcome challenges if the right kind of engineering advancements were made and we assume the political will and budget were not blockers.

It doesn't have to involve humans landing (unless it has to). I just wanted to see if we could get a probe into the water to explore and send back images or videos of anything it finds down there - ideally living creatures.