I "darn" a lot of stuff ... darn this, darn that .....
Seriously, I have darned .... but only if it is something really important to me.
Usually it's socks, and by that time, they really are not worth it, to me.
So then, it is ... No Way Jose!
Darning can be an art ..... and can be quite meditative.
A nice challenge with a huge feeling of satisfaction when done well.
In essence you would be replicating the weave of your blanket.
Find a yarn that somewhat matches the blanket in texture, weight, etc.
Then start your weave in the good part of the blanket to anchor it well.
Skip across the open area and continue into the good part again.
Repeat, with each row close together, and the hole is filled.
All in the same direction.
Then start the cross weaves, emulating the blanket pattern.
Most will be over and under. However, some may be over two, under one, etc.
Continue til all is finished and your hole is filled in.
Soon enough you will be saying ... Darn good Darning!!!
Love your idea of not trying to match the darned piece and working it as a plaid!
Or could do other patterns.
After all, it is going to be different, so why not let it show it's stuff!!!
All the same technique.
Good Luck!!
Happy New Year, Everyone!!