Is it possible to use a line doubler or quadrupler when transferring to the computer to decrease aliasing and then edit from the new source?

Will a computer accept signals from video scalers/converters? What equipment would be necessary for this?

If I'm not mistaken line doublers are analog devices. So you will
need an analog capture board to process such footage. But I'm
thinking anything you can do with a line doubler realtime you
can also do (perhaps not realtime) in post on a computer.

What "effect" or "solution" are you looking for exactly?

I'm looking to smooth out the edges reducing aliasing, so that I may do composites with out any issues.

According to the product description. Th is what the various items do, video scalers/upconverters line doublers and quadruplers. I don't see why they couldn't be used on a computer to create a sort of master copy where it can be edited in After Effects.

Linedoublers are only "eye candy". Very good "eye candy" indeed but not suitable for postproduction. That's why broadcast reference monitors have no built in linedoublers like most TV-sets do. A good YUV signal is better than a weak with linedoubling.