Just something to add, an assumption is the engines are used in multiples of 800G:

1 (4 x 200) Tx engine + 1 (4 x 200) Rx engine used in an 800G module
2 Tx + 2 Rx for a 1.6T module
4 Tx + 4 Rx for a 3.2T module

If it's possible to build an 8 x 200G/lane 1.6T engine, it would cut the number of engines (and perhaps a bit of space) needed for the higher speed modules; maybe even open up possibility of 6.4T.  Since no 400G engines involved, all the above can be manufactured at a new +1 JV if one materializes.