Vim: corresponding colon command to "a" in normal mode

Vim: corresponding colon command to "a" in normal mode

As we know that you can't enter insert mode by
:exec "normal [iIaAs]"
The only way I know to enter the insert mode from colon command is
:startinsert[!]
While the :startinsert performs like 'i' and :startinsert! like 'A'. But
how can I get 'a'? You can't use
:exec "normal l"
:startinsert
because it doesn't work at the end of line.