After MUCH mucking around, hair pulling, cursing and testing. I have created some pitiful few lines of code, that will make the Mig-15's landing gear properly map-able to the "LASTE" 3way switch on the Thrustmaster Warthog throttle. "Up/Neutral/Down", just like the Mig-21 mod you gave me.

First, Make backups of the originals. And a WARNING!!! Do this at you own risk, yadda yadda yadda...And remember I don't know what I'm doing! All I know is it worked.

Second, I used Notepad++ to edit these things after reading many posts over at the ED forums. Do a search for it.(it's free).
Though maybe you can use regular Windows Notepad without problems. I'm not sure.
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The install Path=(YourInstall Dir)\Eagle Dynamics\DCS World 2 OpenAlpha\Mods\aircraft\Mig-15bis\joystick
Add these 3 lines in the "default.LUA" at least after line 15. (I inserted mine at line 35 but I don't really know what difference it would make.)
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--Alternate Landing Gear Handle, Up
{down = iCommandPlaneGearUp, up= iCommandPlaneGearUp, value_down =1.0, value_up=0.0, name = _('Alternate Landing Gear Handle, Up'), category = _('Systems')},
{down = iCommandPlaneGearDown, up= iCommandPlaneGearDown, value_down =-1.0, value_up=0.0, name = _('Alternate Landing Gear Handle, Down'), category = _('Systems')},
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then add these, two groups of 3 lines, to BOTH the "Throttle-HOTAS Warthog.lua" AND the "Joystick-HOTAS Warthog.lua" below the "keyCommands = {" (line #9).
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--Alternate Landing Gear Handle, Up
{down = iCommandPlaneGearUp, up= iCommandPlaneGearUp, value_down =1.0, value_up=0.0, name = _('Alternate Landing Gear Handle, Up'), category = _('Systems')},
{down = iCommandPlaneGearDown, up= iCommandPlaneGearDown, value_down =-1.0, value_up=0.0, name = _('Alternate Landing Gear Handle, Down'), category = _('Systems')},
--Alternate Landing Gear Handle, Up
{down = iCommandPlaneGearUp, name = _('Alternate Landing Gear Handle, Up'), category = _('Systems')},
{down = iCommandPlaneGearDown, name = _('Alternate Landing Gear Handle, Down'), category = _('Systems')},
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Run DCS, map your controls to the new "Alternate Landing Gear Handle,UP and DOWN" and enjoy.
Or, conversely, start swearing at me that it's, "All fucked up now!!!", and reinstall the old files.(you did back them up right?!!)

If you didn't back things up, you're still fine. Just do a "restore/repair" on the game and all will be well again.
Also remember to keep a copy of the modded files somewhere safe because they WILL be over written when ED updates the game.