Hi is ,it possible to add a feature where even if there is something in the offhand the first person model still stays , and it doesnt go back to default vanilla look?

Huh? Thats already the case. If the mod toggles off, then the item you are putting into the offhand is a known broken item like modded maps, so the mod turns off for the map to be viewable at all.

I think you missunderstood. There is a list of items that auto turn on the vanilla camera. Never heard of the Timeless mod, and items from that mod are not on the list https://github.com/tr7zw/FirstPersonModel/blob/main/FPVersionless/src/main/java/dev/tr7zw/firstperson/versionless/config/FirstPersonSettings.java#L20 . So most likely the Timeless mod is just incompatible and still renders the vanilla firstperson view model even when it shouldn't. So far nearly all gun mods are incompatible in some form, and I have stated on other issues before that I won't invest much more time into trying to get some specific gun mod to work. And even then "work" is relative, as people then complain that the sights don't line up from the 3rd person model to the camera, which is to be expected, because the gun mods are not designed to work like this. So it's just a massive time sink to get something "not really working".