All of the flashpoints and 2/4 man heroics should have a scaled version for solo players. Same rewards, same level of challenge but give the ability for all of the working people that have families and lives to get the most out of it.
While I support the idea of creating solo versions of existing content, I *don't* support the idea that the rewards should be the same. If they were, why would *anyone* run with a group? The reason that group content provides better rewards is to encourage people to work together. The content is, generally, still pretty easy and is only scaled high enough that it's difficult/impossible for subnormal group sizes to complete it.
I'm also amused at your "same level of challenge" statement. How do you achieve the same level of challenge for mechanics like the beastmaster on Mando Raiders, where the entire point of the fight is to keep the dogs separated from the boss himself while having to regularly taunt back and have DPS and healers bounce the targets? The only way to create a construct like that for solo content would be to have the boss stand still and just require that the dog be kept out of melee (which would pretty much happen by default anyhow). There are plenty of fights where the entire *point* is to create a situation where the group has to work together in more ways than just "tank and spank", especially when there are mechanics that require explicit action from individual roles: threat drops, tank swaps, boss placement, cleansing, etc.
Solo content is easy because there's not much you can do to make it that hard without making it impossible for some roles/classes to do outright. Group content, because it makes the assumption of certain composition and capability for each role *within* that composition, can create nominally more difficult/complex strategies thanks to having more bodies and guarantees of specific abilities.
So, I support the idea that there should be more solo content, especially solo or small group variants of a lot of the end game H4s (especially the Seeker Droid and Macrobinocular quest lines), I don't agree that they should have the same rewards. The difficulty wouldn't be the same and, even if it were, it would eliminate the impetus for people to actually group up.