That sounds like a great idea! Modifying those two combines to specialize in rice harvesting will definitely make them a valuable addition to the game. Increasing their capacity will make them more efficient for handling rice crops. Offering them at a cheaper price than the base game versions will make them more accessible to players.
Rice harvesting can be a unique and challenging experience in Farming Simulator, so having specialized equipment like the Massey Ferguson MF8750 and Claas Lexion 8900 with rice header edits will enhance gameplay for those who enjoy cultivating and harvesting rice. It would be interesting to see how these modifications improve the performance and efficiency of these combines when working in rice fields.
If you need any assistance with the development or testing of these mods, feel free to ask the community for help. I'm sure many players would be excited to try out these modified rice combines in their virtual farming operations. Good luck with this project, and I look forward to seeing the finished products!