Here's an interesting study from RAND about modernizing US airborne forces:
https://www.rand.org/pubs/research_reports/RR309.html
Basically, their recommendation is to give some airborne units LAVs so they can operate as light armored units behind enemy lines. This gives the Airborne the ability to land farther away from the target and bypass enemy forces to strike over a much larger area. Currently, the Airborne's job is basically to drop within walking distance of the target, seize the target, and defend it until conventional units can link up.
The way I see it, there are three options for motorizing the Airborne:
1. Go with RAND's recommendation and use Strykers or LAVs. This option has the shortest range and requires the most airlift capacity. However, they provide good protection against all types of threats, and they can carry heavier weapons like the 25mm.
2. Use vehicles like the up-armored humvee or JLTV. These provide some protection against IEDs, small arms, and shrapnel. However, they require more fuel and they can't protect against accurate artillery, air attack, or anything heavier than an AK. You could also supplement this force with some LAVs or Strykers to add firepower
3. Use unarmored vehicles like the Infantry Squad Vehicle or MRZR to manuever. This would be the lightest option to airlift, and require the least amount of fuel to keep it going. However, these can only be used to ferry the unit to objectives. Anyone who tries to engage the enemy from one of there is toast. Just like option 2, this force could be supplemented with LAVs or Strykers.
A motorized or light armored airborne unit could be used for more missions than current airborne units, which can seize airfields for follow-on forces and that's about it. Giving the airborne wheels lets them take on missions that you might see a MEU doing OTL, like evacuating US nationals from hotspots or securing WMD sites.