MWR offices on base sell regular MYW tickets, but at a discounted price.
For example, for your situation, the base nearest me is selling 10 day adult park hopper tickets for $419.25 instead of $456.89 that you get at the website or the gate. Savings is $37.64/adult ticket.
Shades of Green also sells Stars and Stripes tickets. Stars and Stripes tickets are, according to shadesofgreen.org:
A 10 day Stars and Stripes ticket, which gives you 10 days for regular park entry as well as 10 admissions to the WPF&M options (excluding mini golf - is $422.00. Slightly more than the 10 day park hopper tickets from MWRs, but for that extra $3, you get 10 admissions to the WPF&M options.
Stars and Stripes tickets can only be purchased at Shades of Green.
Click here for the full price list. I do not know if they are selling Stars and Stripes tickets over the phone or by fax in order to now accommodate for FP+. That you would have to ask SOG directly.
Who did you ask? Disney? Disney phone CMs likely have no knowledge of what base ITT/MWR offices sell, nor do they have knowledge of what Shades of Green sells. The discounted tickets I discuss in this post aren't available through Disney, only through military base ITT offices and Shades of Green.