That depends on ISA's details, honestly. For example, Knuth's MMIX has 64-bit words and has separate intructions to load/store 8-, 16-, 32-, or 64-bit wide chunks of data to/from memory — which are forced to be naturally aligned because 0, 1, 2, or 3 lower bits of the address are masked, depending on the data access's width. So there you go, you have aligned access for all "natural" subword sizes.