This paper presents an improved interconnect network for Mesh of Clusters (MoC) Field-Programmable Gate Array (FPGA) architecture. Proposed architecture has a depopulated intra-cluster interconnect with flexible Rent's parameter. It presents new multi-levels Switch Box (SB) interconnect which unifies a downward and an upward unidirectional networks based on the Butterfly-Fat-Tree (BFT) topology. To improve the routability of proposed MoC-based FPGA, long routing segments are introduced as a function of channel width with adjustable span. Compared to basic Versatile Place and Route (VPR) Mesh architecture, a saving of 32% of area and 30% of power was achieved with proposed MoC-based architecture. Based on analytical and experimental methods, we identified and explored architecture parameters that control the interconnect flexibility of the proposed MoC-based FPGA such as Rent's parameter, cluster size, Look-Up-Table (LUT) size, long wires span and percentage. Experimental results show that architecture with LUT size 4 and Cluster arity 8 is the best trade-off between power consumption and density. It can also be noted that in general long wires span equal to 4 and percentage between 20% and 30% produce most efficient results in terms of density and power.