You can short out C5 completely and then remove D1 and R3, they are only there to protect the trigger input from over-voltage as the TSOP output goes high. None of the measures you suggest will work properly though unless you place a much larger capacitor across the TSOP output, the drawback is it will also make it far less responsive when you do want it to trigger and you would have to limit the discharge current into the TSOP as its output went low.
Brian.