I'd definitely consider Windows Presentation Foundation over Winforms if this inheritance thing is a problem for you, because WPF *does* support that sort of visual inheritance, and i will set you up for WinUI going forward.
Coincidentally, there is also a session about using WPF in Visual FoxPro at Virtual FoxFest that covers some of the fundamentals of WPF and how it's different from VFP and HTML.
https://virtualfoxfest.com/Sessions.aspx#WPF_Modern_UIs_in_VFP_Applications https://virtualfoxfest.com/Sessions.aspx#WPF_Modern_UIs_in_VFP_Applications