One exception to the rule....

On the whole, your logic makes complete sense.

However, if you can only afford only ONE keyboard, and you are a beginner and practicing scales, arpeggio's, runs, fills, etc. would it not be more advantages to practice on a weighted keyboard than a synth weighted keyboard? Once you develop the finger dexterity on that keyboard, moving to a semi-weighted or non-weighted keyboard will make your fingers fly.

Again, if you can only have ONE keyboard wouldn't it be nice to have a weighted keyboard with the features of an exotic arranger?

Just a different point of view...

Regards,
Al G