Besides AMS, what other destinations would you be flying to for work?

The best fit for you heavily depends on where you will most often go. A lot of your flying is to MIL. If there are no direct Skyteam flights, you will probably be bound to Air Berlin on this route. Air berlin is part of OneWorld, as is Finair, Iberia and British Airways.

So personally I would take a look if the OneWorld network satisfies your needs for work and holiday travel. I have heard many good things about the BA Avios program, so that might be worth looking in to.

Alternatively you could fly to Milan using a connection somewhere, or use Easyjet as an alternative direct flight. Easyjet not being part of an alliance will probably make it difficult to reach/keep status with any alliance. However if that offers a substantial financial advantage I would definitely consider it as an option.

Flying with a stop to Milan is going to be tiresome, but it is doable. It has the advantage that you will collect miles faster, and flights with a stop are often cheaper than non-stop. Though I am not sure if that is also the case when both Easyjet and AB are active on your route..