I hope this code can help you a bit, drag and drop it in your VC command tree. It will show you the info panel from a movie, in which you can see the "trailer" button and play the trailer. If you use this command for first time, start a trailer from the info panel one time by hand, then you can use this command for each other movie without pressing the trailer button by hand. Not real elegant but you can play with the code, maybe you will find a better solution.
<?xml version="1.0" encoding="utf-16"?>
<commandGroup open="True" name="xbmc play trailer" enabled="True" prefix="" priority="0" requiredProcess="" description="">
<command id="843" name="Find Movie {1}" enabled="true" alwaysOn="False" confirm="False" requiredConfidence="0" loop="False" loopDelay="0" loopMax="0" description="">
<action>
<cmdType>XJson.SmartPL</cmdType>
<cmdString>smarts\MovieByName.xsp&&{2}</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>VC.Pause</cmdType>
<cmdString>300</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<if ifBlockDisabled="False" ifNot="False">
<ifType>(A)==(B)</ifType>
<ifParams>{1}&&Play</ifParams>
<then>
<action>
<cmdType>XJson.Raw</cmdType>
<cmdString>Playlist.Clear&&"playlistid": 1</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>XJson.Raw</cmdType>
<cmdString>Playlist.Add&&"playlistid": 1, "item": {"file": "special://profile/playlists/mixed/voxsmart.xsp"}</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>XJson.Raw</cmdType>
<cmdString>Player.Open&&"item": {"playlistid": 1}</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
</then>
<else>
<action>
<cmdType>XJson.Raw</cmdType>
<cmdString>GUI.ActivateWindow&&"window": "video", "parameters": [ "special://profile/playlists/mixed/voxsmart.xsp" ]</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
</else>
</if>
<action>
<cmdType>VC.Pause</cmdType>
<cmdString>500</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>XJson.Btn.KB</cmdType>
<cmdString>i</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>XJson.Btn.KB</cmdType>
<cmdString>Return</cmdString>
<cmdRepeat>1</cmdRepeat>
</action>
<payloadList>Find, Search, Show</payloadList>
<phrase>trailer</phrase>
<payloadFromXML phraseOnly="True" use2partPhrase="False" phraseConnector="by" Phrase2wildcard="anyone" optional="False">XbmcPayloads\xbmcMovies.xml</payloadFromXML>
</command>
</commandGroup>