I think this would be a really neat project that is easy to accomplish.
I agree, the pattern is based on the same Spangled Genetic background and diluted with dominant white, If you cross your cream brabanters with Chamois Spangled Appenzeller spitzhaubens the first cross will give you Chamois looking birds right out of the gate, all you need to do is take your best F1 and cross it back to cream brabanters, you just need to make sure you keep the birds with dominant white and none cream.
Cream Brabanters genetic background for the pattern:
ER/ER, s+/s+ ig/ig Db/Db, Pg/Pg, Ml/Ml i+/i+
Chamois Spangled Appenzeller spitzhaubens genetic background for the pattern:
ER/ER, s+/s+ Ig+/Ig+, Db/Db, Pg/Pg, Ml/Ml, I/I
The offsprings of this cross will be:
ER/ER, s+/s+ Ig+/ig, Db/Db, Pg/Pg, Ml/Ml, I/i+ So very Chamois looking, Ig+/ig will make the birds none cream, and I/i+ may show some black specks where white should be, but very much Chamois looking, now the tricky part would be crossing back to Cream Brabanters, you will get none-cream Brabanters, Cream Chamois, Cream Brabanters and Chamois, you will need to breed quite alot to keep the Chamois look going.
If you cross the Chamois looking BC1xBC1 to each other you can expect many None-Cream Brabanters, Cream Brabanters, Heterozygous dominant white Cream Chamois Brabanters(black flecks on white feathers), Homozygous dominant white Cream Chamois Brabanters(no sign of black flecks on white feathers), Heterozygous dominant white Chamois Brabanters(black flecks on white feathers), Homozygous dominant white Chamois Brabanters(no sign of black flecks on white feathers).
That is alot of variables introduced by the cream gene, if I were you I would start with regular gold Brabanters and Chamois Spangled Appenzeller spitzhaubens, that way the only variable will be dominant white, less hatching required to avoid the creams, unless you want cream chamois Spangled Appenzeller spitzhaubens