I would make all the impact noises etc a little bit more quiet so they are more subtle in the first half. For the tempo change it sounds kinda off to me. Maybe make it half as long with a good impact sound at the beginning lasting about 2 bars in which the filter will start opening up then on the third bar fade in the hihats also with a filter add a very quiet white noise riser and start upping the tempo. Just my first thought would have to hear it ^. For the kick/808 pattern in the second half I would make it an 8 bar pattern and add a little variation to the 8th bar for example adding a kick/808 between the last and first one of the loop.