Blast Furnace II - Require Coal on Outer Input for easier upgrading

Goal: Clear and simple upgrade path from Furnace 1 -> Furnace 2 -> Arc Furnace 2
If you require coal on the outer input, when the time comes to upgrade to Arc Furnace II, then 2 inputs will already correct, coal will be disconnected (and not used anyway) and Graphite/water can still be added.
This would also require updating Blast Furnace I to move an input over and put coal there.
Issue: Would affect in progress games.
Workaround: If your able to keep existing buildings as is, but new ones are updated.

I got lucky when I made new builds with Blast Furnace II and just happened to put coal on the outside input, but when I went to upgrade my original Blast Furnace I builds I ran in to the same issue.
I was trying to figure out how to make the two->three->two U-shaped inputs work if the two inputs were always centered; your idea to offset them on furnace 1 is one solution. The other thing is to have Furnace I have three inputs in the same arrangement as Furnace II.