This paper addresses the challenge of pilot overhead reduction in Multi-Input Multi-Output (MIMO) systems employing Orthogonal Frequency Division Multiplexing (OFDM), a promising candidate waveform for future 6G networks. As networks scale with increasing antennas and subcarriers, the pilot overhead also rises, reducing spectral efficiency. Moreover, the stringent reliability requirements of 6G demand a robust channel estimation scheme with minimal pilot overhead. To meet this need, we introduce a Semi-Blind Channel Estimation framework with Adaptive Pilot Design (SBCE-APD) that aims to achieve a target estimation accuracy with minimal pilot overhead. Traditional techniques primarily aim to improve estimation accuracy for a fixed pilot budget. In contrast, the proposed SBCE-APD operates as a closed- loop framework that minimizes pilot overhead subject to a target accuracy constraint. Its main novelty lies in the system-level integration of adaptive pilot-count selection, pilot placement, and semi-blind channel estimation. The method combines two complementary estimation branches: a pilot-based estimator and a non-pilot-based estimator. Their integration forms a semi-blind estimation structure, reducing dependence on pilot symbols. Furthermore, the pilot pattern is adaptively adjusted over the air, optimizing the number of pilots under varying network conditions to maintain the desired accuracy efficiently. Simulation results demonstrate substantial gains in pilot efficiency while preserving reliable channel estimation, establishing SBCE-APD as an effective and scalable solution for 6G MIMO-OFDM networks.