Yes the user can assign MIPI signals across different DQS groups.
The current RD for CertusPro-NX implements the same idea.
Example#1 - MIPI signals across multiple DQS groups: MIPI DSI-CSI2-OpenLDI-LVDS-Int_Bridge
rx_clk_p_i MIPI_DPHY BDQ114
rx_clk_n_i LVCMOS12H BDQ114
rx_d3_p_i MIPI_DPHY BDQS114
rx_d3_n_i LVCMOS12H BDQSN114
rx_d2_p_i MIPI_DPHY BDQ114
rx_d2_n_i LVCMOS12H BDQ114
rx_d1_p_i MIPI_DPHY BDQ114
rx_d1_n_i LVCMOS12H BDQ114
rx_d0_p_i MIPI_DPHY BDQ126
rx_d0_n_i
LVCMOS12H
BDQ126
Example#2 - Multiple MIPI signals in one DQS group: MIPI DSI-CSI2-OpenLDI-LVDS-Int_Bridge
tx0_clk_p_o LVCMOS18H BDQ6
tx0_d3_p_o LVCMOS18H BDQ6
tx0_d1_p_o LVCMOS18H BDQSN6
tx0_d0_p_o LVCMOS18H BDQ6
tx1_clk_p_o LVCMOS18H BDQ6
tx1_d3_p_o LVCMOS18H BDQ6
tx1_d2_p_o LVCMOS18H BDQ6
tx1_d1_p_o LVCMOS18H BDQ6
tx1_d0_p_o LVCMOS18H BDQ30