First a confession: I like to tinker.
Before getting a proper 4x5 enlarger, I was thinking about botching together a negative holder and a light source to turn my 4x5 camera into an enlarger. The other day, I was dismantling a scrap DeVeers enlarger (bought for $12 at a garage sale) to use the columb as a copy stand. I noticed that the negative stage and the lens stage of the enlarger which are held together by a focussing rack looked a lot like a view camera, minus the movements. Well if only I can figure out how to hold a ground glass screen and a roll film back in place, then I've done the opposit - turn an enlarger into a view camera. If nothing else, and I suspect that to be the case, it will look impressive sitting on a shelf.
I like to tinker too, but I hate to waste time. Don't do it. I'd hate to try to take pictures with my enlarger. No movements, etc. Buy a speed graphic at a garage sale and try that. Spend the extra time making photographs.
Save a lot of trouble and get a used Bessler or Omega from Ebay. You have to consider how you can keep your rig square to the easel, negative carrier square to the printing frame, how to attach the light source, attach the camera to the chassis etc. Used enlargers go real cheap on Ebay now. Look at the past history of sales and then set a price you are willing to pay.
There are lots of cheap enlargers out there, so no real reason to cobble something together.
That said, the largest enlarger I have room for in my little Manhattan apartment is a medium format enlarger, so for 4x5" I use a Graflarger cold light back on my Linhof with a copy stand, and it's pretty good. The Tech V is rock solid, and I can use the camera movements for small perspective corrections when enlarging. I use a conventional enlarging lens mounted on a Linhof lensboard.
In any case, you can find Graflarger backs that will attach to any 4x5" camera with a Graflok style back for under $125 usually. Aristo will even upgrade the tube for around $100.
For larger negs than that, I contact print, though I could rent darkroom space if I wanted to enlarge from 8x10".
I have a Speed Graphic and I now have a Beseler enlarger. I'm only playing at this for fun. Like I said, the new view camera/enlarger part will probably just sit on a shelf, but if I ever get a negative made by it, it'll "taste a bit sweeter."