I would look at the LNR rigs. The MTR 3B is very small and light. The best spec. is that it draws only 35 ma on RX which is very important and only about 1/2 amp on TX. I have found that a power of 2 to 5 watts is plenty for me on many of my QRP expeditions since the 1950's and 20 and 40 meters have been the bread and butter bands. So 40,30,20 meters and 2.5 watts should satisfy many of your requirements. My favorite QRP rig for the last 15 years has been my Elecraft KX1 which I usually run on the internal batteries and the 1.5 to 2 watts has proved very satisfactory for most of my operations in the field, especially years ago when the sun actually had some spots. For your type of operation the 500 Hz filter should be very acceptable and I often prefer something between perhaps 400 to 1000 Hz as a good compromise for casual operation, not in a crowded contest from the home QTH. I do not have a LNR but I built a similar rig with push button tune and frequency input with the paddle. I was about 75 years old at the time, but found it easy to master this instead of a knob VFO and even used it in a contest and I could quickly go to a frequency with the paddle then move around with the push button. The ham I built it for could not master how to work it so he donated it back to me. The disadvantage of something like the 3B is that there is no built in battery and no built in antenna tuner. For me these were important since putting up resonant antennas or having an extra item with the external battery was not what I wanted. These things may or may not be important to you. When 15 and 17 meters open up more, these could be very good bands. Some years ago I had a one watt home brew rig on 15 meters. I easily made good QSO's, usually 2000 to 4000 miles, in fact I was more successful than on 20 meters when I ran 4 watts. Part of the reason was that on 15 and 17 it is less crowded and the WARC bands do not have contest QRM, but bands higher in frequency than 20 meters are open many fewer hours a month. Many folks prefer a full 5 W QRP rig, and there are times when I also wished for a extra dB or two.
I now have a KX2, but it is expensive and much heavier than minimal rigs. I probably will not take it on long hikes or on our trips to Europe, etc. since for me ham radio is not my main reason for traveling, but visiting family and friends in several countries and states is my priority. With a very small light rig, I can take it along and if I find I have an extra hour or so once in awhile great, but if not that is fine also. I may buy one of the very light rigs if the KX1 gets too big or heavy !! Have fun, enjoy your portable CW operations. It has been the highlight of my 67 year ham career. Rick KL7CW