After knowing that it is common practice for Europe to wire 2 F20T12 tubes in series off a 220v-240v F40T12 preheat choke, I am wondering if there is a way to use a North American 2 lamp F40T12 preheat ballast with a starting compensator as a 4 lamp F20T12 preheat ballast with 2 pairs of F20T12 tubes wired up in series on both the lead and lag sides of such ballasts while ensuring proper cathode preheating?

You would need the compensator winding split in two.
So no proper heating.

By the way the European preheat circuits do not provide proper preheating either, hence the life rating on the lead side uses to be shorter (about 1/2 till 2/3 of the normal rating; e.g. 16k on lead side and 24k on lag side)

Even a pair of tubes wired in series with their own starter loops does not provide proper preheating too?

The thing is, when you short out the tube (as the starter is essentially doing during preheat), the standard ballast gets slightly sarurated so the current becomes larger than normal arc current, usually about 1.5x. So on a 36W choke the preheat current is around 0.6A. Therefore the filaments of 36W or 18W lamps are essentially designed to be preheated by that current, not the 0.43/0.37A.
But the lead section tends to stabilize the current at the normal arc level, so just tye 0.43/0.37A (for 36W/18W lamps). And that is essentially 2/3 of what the filaments are designed for, so start not preheated enough hence the shorter life rating.
The starting compensator is an extra inductor or a secondary winding (coupled to the rest), which boosts the current during the preheat from the normal arc current level (0.43A) to what essentially the filaments are designed for (0.6A in the F40 case). But standard European lead-lag circuits do not use them as it would need extra bulky and expensive choke, so the insrallations thus live with the shortened life rating.
Anyway the life rating is based on 3h ON per start cycle, while most such office installations are kept the whole shift, so 8h ON per start, so in real life the lifetime difference is not that big and it is within the normal piece-to-piece variation spread.