The BiCu2(P1-xVx)O-6 system shows the appearance of various phenomena that progressively change as a function of the average (P/V)O-4 groups size. Then, from x) 0 to x approximate to 0.7, a solid solution exists with respect to the basic orthorhombic unit cell of BiCu2PO6. For greater x values ( 0.7 < x < 0.96), structural modulations with incommensurate q vector that slightly change versus x appear. The 4-D treatment of single-crystal XRD data of the modulated phase corresponding to x = 0.87 at 100 K ( orthorhombic, a) 12.379(3) angstrom, b = 5.2344(9) angstrom, c = 7.8270(14) angstrom, q = 0.268(3) b*, super space group: Xbmm(0 gamma 0) s00, X stands for the nonprimitive centering vector (1/2,0,1/2,1/2), R(obs)(overall) = 5.27%, R(obs)(fundamental) = 4.48%, R(obs)(satellite)) = 6.58%) has evidenced strong positional modulated effects within the [BiCu2O2](3+) ribbons while three XO4 configurations compete along the x(4) fourth dimension. There is no P/V segregation along x(4) in good agreement with steric-only origins of the modulation. Finally for 0.96 < x < 1, two phases coexist, i.e., BiCu2VO6 ( X) 1) and a modulated phase of the previous domain. The BiCu2VO6 crystal structure shows a unit cell tripling associated with monoclinic symmetry lowering. The VO4 orientations between two ribbons proceed with respect to the interribbon distance. Then the full system shows flexible interactions between modulated Bi/M/O-based ribbons and surrounding tetrahedral groups, depending on the average XO4 size. Furthermore, between two ribbons the Cu2+ arrangement forms magnetically isolated zigzag copper two-leg ladders. Our preliminary results show a spin-gap behavior likely due to the existence of true S = 12 Heisenberg two-leg ladders. Modulated compositions are gapless, in good agreement with band-broadening toward a continuum in the magnetic excitation spectrum. The continuous distribution of Cu-Cu distances along the rungs and legs of the ladders should be mainly responsible for this magnetic change.