Using first-principle methods, we characterized ArmBeOq+ (0 <= m <= 3 and 0 <= q <= 2) and BeOq+ (3 <= q <= 5) multicharged ions (MCIs). This includes their structural parameters, relative stabilities and vibrational wavenumbers. Our calculations confirm the existence of the ArBeO complex. In addition, we found (meta-) stable neutral and ionic complexes such as ArBeO+, ArBeO2+, Ar2BeO, Ar2BeO+, Ar2BeO2+, Ar3BeO, Ar3BeO+ and Ar3BeO2+. The analysis of the structural parameters and of the electron density differences shows that a strong perturbation in the electronic structure of the BeOq+ (q = 1,2) moiety occurs upon complexation, resulting in a major increase in covalency of these multicharged ions (MCIs). The consequences of solvation of MCIs in argon matrices are pointed out. More generally, the effects on the spectroscopy of MCIs trapped on cold matrices are discussed.