You are not going to work all bands portable very well,
unless you are not so portable...IE: the best overall
single antenna for 40-10 would be a 40 meter dipole fed
with ladder line to a tuner.
But you have to drag a tuner around...
Add 80m? Make that a 80m dipole...VHF/UHF? Add a dual
band antenna for those....Again, less portable...
I guess it depends how portable you really wanna be...
I assume that is sort of a backpack rig...
If I were toting a backpack rig, I decide on what bands
I wanted, "within reason", and concentrate on those...
Probably the lightest dipole to cover all bands would
be a 80 dipole, that has insulators to break up the
antenna for all the higher bands..You would have to
manually change jumpers to switch bands, but the antenna
would be very efficient on each band. You could feed it
with rg-58 to save weight. That can be rolled up and
thrown into a pack no problem.
Of course, you would need some trees to throw
it over, or string it between...Myself, I'd be avoiding
verticals running portable QRP...You don't have time to
lay out radials, etc, to avoid ground losses...
For VHF/UHF, hummm, maybe some kind of roll up dual
band J pole or something...??? It's hard to say,
without knowing what level of "portable" you will be...
IE: my level of portable is sitting in/beside a truck,
with the various available facilities I have with it...
IE: I have drive on mast ramps,masts, etc, etc...
I can put up a VHF GP at 20 ft, piece of cake...
If you are packing it, you won't have all that...
I'd keep it simple and low loss being you are QRP...
MK