the force organisation chart

Is designed to be a limiting factor obviously.  And to stop you bringing overly stupid amounts of powerful elite units.  Which it does an ok job of.  And you can get realtively large armies without filling everyslot.  I don't think any army is overly limited at 2000 points.  Theres always a slot empty, and it's doing it's job, forcing to you to balance your list somewhat.  Unlike at say <1500 3="3" and="and" codex="codex" elites="elites" every="every" heavy="heavy" is="is" just="just" mim.="mim." of="of" one="one" or="or" p="p" stakes="stakes" strongest="strongest" the="the" troop="troop" two="two" when="when" wherever="wherever">
It's always been suggested in the 3 rulebooks prior to have second detatchment at above 2500, as yes it can be difficult to get that high in some cases.

And then GW go and ruin it by letting you take a second chart at 2000 points.  They may as well just delete the chart altogether.