I'm pretty sure you still can. The aclient.inp file has to contain all settings though I believe, the changed ones alone isn't enough. I used to use a "Destination path" of setting:aclient.inp
But rather than try and keep an aclient.inp file up to date I prefer to have a DS job with the reg key change and run that.
set NewDS=172.27.24.104
reg add "HKLM\SOFTWARE\Altiris\Client Service" /v DSIp /t REG_SZ /d %NewDS% /f
reg add "HKLM\SOFTWARE\Altiris\Client Service" /v TcpAddr /t REG_SZ /d %NewDS% /f