Imo there should be something like quest or milestones for Science. Like "Create space station 100km above Kerbal with at last 100 parts, using 3 docking port and assemble it in space" for 100 or more Science or "Create Mun base with at last 100 parts (or with 5 research equipment) using 3 docking port and assemble it on Mun" I mean, there should be Science for assemble space station on orbit etc. Or even rescue mission, random spawn Kerbals in crash lander on Mun and we have to rescue them for Science
