Yes, i fully understand. I have two ETRSi and one ETRS (silver), plus the 40/4 MC, 50/2.8 MC and PE, 75/2.8 MC, EII, and PE, 105/3.5 MC, 150/3.5 PE, 200/4.5 PE and the 1.4x PE teleconverter. Plus some accesories like the Motor Drive E (the original).
BTW, i don't know how many lenses do you already have, but the 150/4 (early mc) has an unfair reputation of being a "bad" lens. It is a very good lens, really.
If you don't like heavy weight, don't use the Motor Drive E! It weights about 900g or so and uses 8 AA batteries. I bought it because it's the only one to give you electric shutter release, which also allows it to have a remote cord connection. All the later 'winders' don't have a remote connection, nor electric release. Otherwise they're better in every regard.
If you're using the WLF, be careful. I carry my ETRSi inside my camera bag and one day, the WLF de-attached itself from its place (it's easy to push the viewfinder release button) and started scratching the focusing screen. Now I have a scratched focusing screen. The prisms, having more mass, seem to be more difficult to de-attach.
Additionally, the WLF has no protective glass between the focusing screen and the environment. I find this a design flaw on these (otherwise great) cameras. Dirt, grime, etc, thus easily gets inside the fresnel grooves. The Pentax 6x7, the Mamiya RB67 and C330, all of them have a protective glass over the focusing screen.