I always liked Space Empires V for the vast technologies it offered and what comes with it the diverse paths you could take in development.

While implementing such a vast tech three could be an overkill it would be great to be able to take very diverse paths in technology.

Another thing that you almost always face is reaching a limit. Having mark 3 lasers / armour or what ever. You know you now have the biggest gun the game can offer.
It would be great if that was never the case. Allow for technology to develop without limits.
This would most certainly be an impact on how science victory would look but I think it is something to consider.

While in principle i love the idea, i'd say that for the sake of being able to end the game it should remain fairly close to how it always has been. Not to mention how overpowered science based factions may become from a system like this

I don't expect there would be an overkill by science races just like there is none with what is proposed in earlier games.

Competition doesn't sleep and the best progress usually has the largest race that simply has the biggest science income.
Maybe this would be even a better incentive to create aliances and research together.

If you provide a vast array of arsenal (drones, capita ships, fighters and so on) that is strong against one type but week against another this wouldn't be a problem.

Just like rock, paper, scissors. (but with more components)

Rock will would win with paper only if it would be a very very big rock.

If you carefully taylor the cost of emergent prototype (be it for systems or ships) you can limit the pure raw advance in science. In some games, unlocking some deep technology step can be a waste of resources, if you don't have secured the areas for the new resource, have the industrial capacity for new weapons or hulls for instance. 

I think representing a bit the advantage of the true and tried approach wouldn't be too bad. We can easily see irl how very complex systems can be hindrance in their infancy. Costly prototypes (or random issues) or some slight bonus when producing vintage designs could be a thing, for instance.

After all science in 4X is often something that can spiral out of control.