3-4 annual MUC-US are nowhere near 1P (Premier Exec). In the best case, we
talk about 11K miles per return, so the OP would have to do additional runs
to turn golden.
Also do not forget that LH silver (FTLs) DO get access to the LH lounges. A
very compelling reason for people who fly a bit but regularly to join the unloved
Miles&More.

But if the OP considered to book his or her LH, LX, DB, SK runs within Europe
to MP as well then 1P is definitely preferrable over LH's FTL.

If you know a 1K Hippo72 you could also obtain PremierAssociate level
from him or her, maybe even Premier.
The trick would then be the same omnisapient qasr stated: use the MP
number to reserve seats and upon check-in or at the gate switch to your FTL
account.