I texted a friend about it last night and he told me that the 105MM (M119A2) can be carried internally on the CH47 but it's easier to sling load them.That is a great question. As @Hotdogs notes it is nothing new, but the numbers (by my feeble estimate) are kind of interesting when one thinks of a peer-to-peer fight. I imagine it would take six to 8 CH-47's/MV-22's to lift a single 155 battery with ammunition - 24 plus to lift an entire battalion. Of course artillery battalions aren't sent anywhere alone, so you have already moved at least two infantry battalions (each with mortar capability). On top of that you have to add in CAP to cover the lift (or would HMLA do the job...maybe both?) and a nearly continuous logistics. Now the Corps work on a fully autonomous Huey (and K-Max) makes sense.
Of course, we don't every have a need to go from an LHA to land, so we have that going for us.