I recognise your conundrum! Many years ago I had the opposite decision to make and eventually traded my Beogram 4000 for an LP12, a decision I now regret.
You ask about the Beogram 3000 and the Beogram 1202. They are mechanically the same deck, the differences being the platter and the cover, where the 3000 wins out by dint of better record support and an elegant hinged cover. The best cartridge for either turntable is probably an SP12, with its elliptical stylus. The 1203 is a different deck altogether and is not such a good performer. However, I’m not sure i wholly agree on your view that the Beograms would be more appropriately contemporary with the 33/303 - which is from 1967 - than the Linn. All 3 turntables were introduced in the same year - 1972. Arguably the design ethos behind the Linn is more in keeping with the Quad 33/303 combo, both being excellent ‘engineering’ designs rather than the more ‘stylised’ Beograms. The other factor is, of course, sound quality. Your M100.2s are outstanding speakers with excellent bass performance. They’re certainly good enough to show the disparity in performance between the Linn and the two Beograms, providing the Linn is still well set up, which raises another consideration.
You mention the Beogram 4002 and refer to its ‘complexity and reliability’. One of my many regrets in selling the 4000 and getting a Sondek was that the Beogram was to all intents and purposes a ‘plug in and play’ deck. The Sondek required a lengthy set up process and I was always concerned that it wasn’t performing as it should. Eventually I returned to a Beogram and other B&O equipment and stopped worrying about the HiFi and just listened to the music.
The 1202 and the 3000 are both reliable decks and not too complex, certainly less complex than the 400X series. However they’re both nearly 50 years old and finding one fully working, with a good SP12 cartridge/stylus and in good cosmetic condition will be a challenge. If your Linn is in good condition you should be able to sell it for more than enough to fund the purchase of a 3000. Perhaps any surplus could part fund a Beomaster 3000/4O00/4400 to complete a full Beosystem. Mind you, I’ve owned a Quad system (34/405/ESL57) in the past and they’re excellent, reliable, well-designed products so I would understand any reluctance to part with the 33/303.
Cleve