"A Bishop on a4 could move along c5-d6-e7-f8 but not b5-c6-d7-e8. For a Bishop on 4 the reverse would be true. But that also means a Bishop on a4 can only be captured from c5 -d6-e7-f8 and not from b5-c6-d7-e8.
If this is true the ...."
This is absolutely correct when considering the squares of a switch as separate squares. This looks different if the switch is seen as a unit. But that's a convention that needs to be met. I have already described my intention, but it is not an absolute requirement.
"The issue of teh Knight is really an independent one. If the Knight's move is defined 'subtractively', by excluding moves that a Queen can do, its mobility is reduced in the vicinity of the switch, as Q gets extra moves there. In a 'constructive' definition of the Knight move, it would benefit from the switch topology to get extra moves as well."
Exactly this consideration speaks for a separation of the fields 4/a4. A knight starting from 4 via a5, a6 lands on b6. With a switch as a unit, b6 is on the same line. With 4 as a separate square, b6 is not on the same line. For a4 vice versa. That would be my consideration. I'm thinking of novice players who will notice exactly this inconsistency.
"A Bishop on a4 could move along c5-d6-e7-f8 but not b5-c6-d7-e8. For a Bishop on 4 the reverse would be true. But that also means a Bishop on a4 can only be captured from c5 -d6-e7-f8 and not from b5-c6-d7-e8.
If this is true the ...."
This is absolutely correct when considering the squares of a switch as separate squares. This looks different if the switch is seen as a unit. But that's a convention that needs to be met. I have already described my intention, but it is not an absolute requirement.
"The issue of teh Knight is really an independent one. If the Knight's move is defined 'subtractively', by excluding moves that a Queen can do, its mobility is reduced in the vicinity of the switch, as Q gets extra moves there. In a 'constructive' definition of the Knight move, it would benefit from the switch topology to get extra moves as well."
Exactly this consideration speaks for a separation of the fields 4/a4. A knight starting from 4 via a5, a6 lands on b6. With a switch as a unit, b6 is on the same line. With 4 as a separate square, b6 is not on the same line. For a4 vice versa. That would be my consideration. I'm thinking of novice players who will notice exactly this inconsistency.