Not heard anything @ MG releasing any figs, but I can recommend grabbing some Tamiya 1/48 scale figure sets and exploring conversions. The German tanker sets (for example) have guys in coveralls that should look the part - but I have no knowledge of what outfits the dudes wear in the 'Metal Gear 'verse'. But the Tamiya (and ICM) 1/48 scale figures are of excellent quality and sculpt and so should be a great basis for conversions. Plus, being injection molded plastic, they are easy to work & inexpensive.
Regards, Robert