[TOS'd]

I don't think you are going to get everything with one company. Also you may want a lawnmower which requires like a 7.5 Ah battery to operate for a decent amount of time. But are you going to want to use a 7.5 Ah (large and heavy) for a handheld power drill? Likely not.

If that's the case then maybe stick to one brand for your everyday essential smaller handheld tools that will only really need the smaller 1.5 Ah or 2.0 Ah batteries. And then if you have to branch off for the larger more niche items then that could be a good compromise.


EDIT: The large 7.5 Ah for the lawnmower is a 40V vs the smaller ones for the handtools are 18V. So I don't think you can even mix and match those anyways. But my suggestion still makes sense.