Unless you are 'consuming' 2-4 quarts of oil between gas tank fillups and want to catch the oil and pour back into the engine, why bother?

Your PCV system is quite good at routing crankcase oil vapors back to the intake to be burned. Less than 1 quart every 5,000 miles is pretty good in an older car. If you have a catch can, not all of the vapors will condense into liquid oil, plus you will then have something else that needs attention every few thousand miles. Along with an air freshner for the cabin.

I doubt many enviro testing stations will approve of the modification.

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Keeping it running is better than buying new

My question--why would you need this? I've used a catch can (home made) on my sometimes track car 144S -- but that involved running near redline for much of a lap on the track and reduced the chance of leaks at the crankshaft seals.
HERE'S A CATCHCAN STORY -- My Danish friend Gert joined his friend with a Model A Ford which they drove from Denmark to Italy. Well on their way, it developed a severe rear main seal leak. The answer was to hang a bucket under the chassis and refill the crankcase every once in a while with the drippings :-)
BTW--my 1980 245 M46 with over 300k will use less than a pint between NY to NC and back. -- Dave