That means SLS will have to solely support the cost of three different engine programs: the RS-25e, J-2x, and the "F-1b."
Actually, it's worse.
It will have to support:
1.) 5-Segment ATK Solids
2.) RS-25D (use up historic Shuttle main engines)
3.) RS-25E (all new expendable)
4.) RL-10B-2 (Interim CPS based on DCSS)
5.) J-2X (for the ultimate EDS)
6.) Whatever is picked for 'advanced booster'
Same issue with the various core components:
Two Boosters (ATK-5 Segment and whatever replaces it)
Two Upper Stages (DCSS and whatever replaces it)
There was to be also two core stages; one with four RS-25D, then transitioning to one with five RS-25E; before they realized how dumb that was and decided to start it off with five engines from the beginning.
Under these circumstances would it not make more sense, even though it may delay flights several years, to simply fly an updated Saturn V.
NASA actually did look at this during SLS studies.
There were three trade groups:
RAC-1: Basic Shuttle Derived Vehicles. These guys won; SLS is the result of this.
RAC-2: Kerolox vehicles. Their final was I think a monolithic inline similar to Saturn V.
RAC-3: EELV Group; their proposal was to cluster a lot of Delta IV or Atlas V cores together.
RAC-2 had lower per flight costs; but higher overall up front costs to develop; while RAC-1 had higher per flight costs, but cost much less to develop.
So due to that, and along with the Congressional "Thumb on Scale" mandate to use STS components "where practicable"...NASA repeated the same mistake they made in the 1970s when picking the final STS design.
Uprated Saturn V we get 130 metric tons.
Uprated Saturn V we get 262 metric tonnes to 100 n.mi and 99.8~ tonnes to TLI with the SAT-V-23(L), which lengthened the first and third stages [MS-IC-24(L) by 20 feet and MS-IVB-24(L) by 16.5 feet] and added four 260" LRBs, each with a pair of F-1s.