Legacy tele primes.. Pentax-M 1:4 100mm ?

Hello all,

Long time lurker first time poster. Love these forums and find them a superb knowledge resource.

I love landscape photography, and I love hiking and camping. I am, however, very much an ultralight packer. Base weight 5-9kg depending on season for camping. Do the occasional 'harder'core bikepacking trips. Love bagging munros on the weekend (though I've only knocked off 30 so far, long way to go!)

The ultralight mentality has transferred over into my photography. I like to pack light, never bring a tripod, and a minimum of lenses. Currently my go to set up is the X-E2 and the XF27mm, I love this combo, and rarely wish for a wider lens in the mountains. I have, however, been missing a longer FL lens.

I had been humming and hawing over picking up a fuji x telephoto. I even ordered a XF 55-200mm but cancelled the order after being told it was not in stock. My father has a copy of the XC 50-230mm but I don't like borrowing gear if I can help it! It is suitably sharp for my needs but I don't like the plastic mount nor lack of aperture ring.

So I got to thinking, do I really need a zoom? What about a longer prime? I love primes, and for landscape I don't mind shooting MF. What about a legacy lens then? My only requirement is that a legacy lens is passably sharp stopped down (ie no haze or super soft corners) and that it isn't going to bankrupt me (so leica glass is out okay!!)

From a bit of research, I have turned up two options:

Pentax 100mm f4 Macro, or, Contax Carl Zeiss Sonnar T* 90mm F2.8 G

The obvious strength of the Pentax is that it is a macro! If I don't like it as a long walk about lens I can keep it in my collection for its intended purpose. The extension tubes are cheap (£30) to bring it up to a 1:1 macro. Reading reviews it seems passable for general duties. It's also super cheap, the lens and adaptor is circa. 100£ . There are also a bunch of other Pentax K mount lenses that are pretty cheap, inc 35mm and 50mm. Just a pity their 20mm is pricey, I'd love a fun manual focus 28mm equiv lens also.

The Contax on the other hand, is the dark (well, silver) horse. Great optics, aesthetics and weight. But its x3 the cost of the Pentax and would require a metabones adapter which is more expensive than the cheaper 3rd party pentax adaptor. At circa £300 all in its starting to exceed what I'd be comfortable spending as an 'experiment'. I mean chuck in a few extra hundred and I could just grab a Fuji XF90mm.

Can anyone advise me one way or another? Any other lens / systems I should consider?