Not quite that, but have you tried https://www.nexusmods.com/mechwarrior5mercenaries/mods/543?tab=description ?

If it works, it should let you pay C-bills to exceed your negotiated salvage points during the post-mission loot picking. It's still "buy it then or not at all" rather than leave it in the market for a somewhat longer window, but it's... in that direction, anyway.

That sure is in the general direction I was hoping for. But i don't like using Nexus these days unless i have to. Either way my question was answered so thank you very much.

There is also a mod that instead of grab bagging random stuff from the battlefield it outs EVERY SINGLE. non destroyed item into salvage list. Gives pages of salvage options on long warzome missions.