Re: Multi-purpose trailer ?
	
	
		So, research should include:
Asking people in places like here what features you should get for the roles you want. 
Look at photos/other trailers and write down the features you like. Visit the local servo with hire trailers. Measure them up and make more notes. 
If you have someone make it for you, get a written quote, with all the features listed. They will also match the drawbar level with your vehicle
A few things I had incorporated into a trailer I had made (purpose: not too 4wd camping, carting wood, dirt, furniture, bike transportation, stuff. 
I ended up with a 7x4 with high sides. 
Removable cage, cage door opens front and back (could use it with no doors on. 
Removable drop down front and rear
Led lights
Longer drawbar (originally for pushbikes to be carried across the front -  not so great for 'off road' use. Also it sits further back from vehicle and doesn't fully enjoy the slipstream
Swing down jockey wheel
Canvas tarp for both cage when fitted, and another for when it is removed. Canopy bows fit either
Tie down rails all round
Mechanical disc brakes (easy to fix on the run
Wiring travels to lights via small square steel section welded to bottom of trailer
Checker plate floor
Wish list: internal tie downs 
Back door of cage *almost* fits in place of rear tailgate and could be used as a ramp with a bit of planning
Sorry for the formatting - tapatalk