By February 1944, the designation "Hornisse" ("Hornet") was finally assigned to the Me.410A planes, and several "factory conversion kits" (Umbausätze) were developed for them to increase their firepower or ensure that they were able to perform various special missions.
The U1 kit, used both on high-speed bombers and "destroyers" (the Me.410A-1/U1 and the Me.410A-2/U1), allowed mounting one Rb 75/30, Rb 50/30, or Rb 20/30 camera onto the central fuselage.
The U2 kit, for high-speed bombers, consisted of a WB 151 ventral container with two additional 20 mm Mauser MG 151/20 cannons with 250 rounds each, in drum magazines. The cannon container was installed in place of the Me.410A-1/U2's bomb bay.
Me.410A-2/U2 night fighters had not only WB 151 containers but also a FuG 220 radar with dipole antennas in the forward fuselage and flame arresters in the plane's exhaust pipes.
The need to repel American heavy bombers running daytime raids over Germany forced the Luftwaffe command to search for a way to arm Air Defence Force fighters with powerful large-calibre weapons. And so, an R2 version of the Rüstsatz kit was developed. The Me.410A-2/R2 had its 7.92 mm Rheinmetall-Borsig MG 17 machine guns removed and a pair of 30 mm Rheinmetall-Borsig MK 108 cannons mounted in a WB 108 container in the bomb bay. The planes were also fitted with ZFR 4a telescopic gun sights.
An exotic weapon was tested on one Me.410A-1: a 210 mm, six-chamber WGr 21 revolving rocket launcher. The launcher was assembled in the bomb bay, with one of the launch tubes protruding beyond the contours of the fuselage. Since the drum rotated quickly, all six rockets could be released at the target in one gun run. The first test fire, performed in February 1944, proved to be unsuccessful, but fine-tuning of the weapon continued. The revolving launchers were mounted on several more Me.410 planes for operational service tests, but the idea never progressed any further.