I think the premise that it's viable to "concentrate together when needed" is false. A key tactic on Ukraine's front line, due to the nature of the enemy and the nature of Ukraine's weapons, is dispersion. Concentrating force for any reason before Russia's overwhelming artillery has always proven costly. When that premise fails the utility of point defense like Gepard fails. The only way to salvage it is to imagine Gepards in quantities that a.) don't exist and b.) can't be crewed for lack of trained manpower.

I seek a larger force multiplier: a system that can effectively cover large areas by a small number of men at low cost. One Gepard could pay for many light fox hunting UAVs. With sufficient autonomy a large number of these could be operated from secure areas by small crews. The system should be capable of reaching behind enemy lines to preempt UAVs before they reach combat areas; a capability the can't be matched by any point defense.