We kind of suspected this, but we have training sims that need the side window support, so our bad luck!
Are you sure that wideview does NOT work with the current Esellerateengine.dll ?
We had similar reports from the key2mouse program from the same developer, and it also had the same issue: it comes with the old XP-only version instead of the current one that supports BOTH XP and Windows 7+, but the key2mouse program works with the new Esellerateengine.dll, so it's possible that wideview would as well. Have you tried to do what I've suggested ?
But even if it doesn't work, the correct solution is not asking us if the scenery could work with the older Esellerateengine ( it can't ), if Wideview is the one at fault here, since it installs the older Esellerateengine.dll which is not even supported anymore by Esellerate, you should ask the developer to update the program to support the correct version.
Is not just FSDT, it's also Flightbeam, Qualitywings, Flightsim Labs, and soon you'll see other developers all using Esellerate, and they ALL obviously use the current version, EXCEPT Wideview.
It's like asking anybody out there to support an outdated FSUIPC, just because you have ONE developer that hasn't updated its products since 2007, it's just wrong. Yes, the *current* version of Esellerate has been released 7 years ago, it's not they didn't had the time to update to it...