I believe that the current requirement of using a hazmat suit instead of a jetpack creates an incentive for using jump pads and walkways at later points in the game. Many players seem to simply ignore these options(especially walkways) when they get the jetpack.
While I agree that we should have some sort of protected building options(floors & walls), I don't think using 'lead' would be the best option. Lead would require a whole new production chain, including new resource nodes all over the map. However, it's possible that we might be able to use some sort of combination of existing materials to create those protecting building options.
In 'the real world', there are a few different elements which have some radiation-protective properties. Most of these are not currently available in the game, but alloys with similar properties may be usable. From some light research, common elements for radiation-protection include: tin, bismuth, and tungsten. Apparently, activated charcoal also has some radiation-resistance, though it's certainly not total resistance(only about 50-70%, IIRC). Additionally, there are some articles denoting silica as being somewhat protective.
Perhaps in this highly futuristic game world there is an improved process by which coal(possibly compacted/enhanced coal), silica, and concrete can be used to create a protective building material. This process would not require any additional resource nodes to be scattered about and yet would still require additional assembly and manufacturing buildings be used for new production, which would in turn use more power and further justify the creation of nuclear power plants.
As a final note; we do not currently know for what S.A.M. ore is used. It's possible that it also has some unique radiation protection properties. It may be forthcoming in Tier 8 or higher. With nuclear chains available in Tier 7 and radiation protection in Tier 8 or above, there would be incentive to first create nuclear power plants far away to supply necessary power and later allow the creation of protected building materials, allowing factories to be expanded to support nuclear chains within.
These are just a few ideas thrown together to provide options for developers that would require less work than creating new resource nodes all over the map in addition to new production chains. A few additional recipes, and few additional textures, and a copy & property addition for a few existing game objects is much less work than would be adding a new resource, which would still require all the aforementioned modifications.