This improvement proposed is to accept column mapping for few or all columns in underlying storage tables - which allows column to be different in underlying storage than column in fact/dimtable
Fact1 has col1
S1_Fact1 has col1
S2_Fact2 has col1_variant
S2_Fact2 can have column mapping property specified as col1:col1_variant. If S2_Fact2 becomes the eligible storage table, then query should be written with col1_variant if col1 is queried.