Here's a thought.
Say I have a unit of 20 slugga boyz. I want to advance them up the table as part of a pretty standard ork army, which includes some faster and some armoured units (so they won't be the only things getting shot at). I intend to use the boyz to fight up close, and I have a smaller unit behind them for mobbing up and as a second wave to bolster my attack.
Standard procedure would be to stick a load of grots in front of them, to give them the 5+ cover save from enemy shooting through gretchin. However, I would need a lot of grots - 15 to 20, perhaps? - and they would soon add up in points.
I notice from the army list that a mek can take a kustom field for 20 points, which also gives a 5+ cover save. I could get 7 grots for 21 points. So, why not make the supporting unit burna boyz, give them a mek with a field (about 35pts in total to upgrade and equip), and put them behind the sluggaz so that the field covers both units?
I've never seen this done and, pie-plates aside, I wonder why not. Any thoughts, anyone?