Yes, but what's happened now? Remember that NSP, before they broke away from the SDA, was the junior partner in the SDA. Today you wouldn't really say that the NSP is a smaller party than the SPP? Sure, the NSP was boosted by people from the Refugee Party, but the RP almost became part of the SDA too, didn't it?
And the INP was the larger party but not by a big distance. It certainly wasn't larger than the islamist and communist factions put together.
It's quite interesting that you are arguing for my case because if the leading parties were majority by a tiny bit, what more when WP has 7 seats + 2 NCMP seats while SPP has 1 NCMP seat and the rest has none, and some begrudge WP for heading a coalition.
I am sure SDP having no seat but telling WP exactly what to do will not be right either, based on the same standards.
There are many more examples where the largest presence in the house heads a coalition. UMNO heads BN and the PM is from UMNO, Conservatives lead the Con Dem alliance and Cameron not Clegg is PM, Liberals lead the Lib-Nat alliance and Abbott comes from Lib, BJP leads India's ruling coalition, Pheu Thai leads a coalition and Yingluck is from PT. I'm picking more norms than exceptions.
The WP - well let's be frank about its strengths. So far they've done well. And one of the appeals of the WP is that the leadership actually acts like grown up people, doing the right thing by not conducting piss fights with other opposition parties (although the same is not apparently true for the rank and file). Firing Yaw Shin Leong when it's time to fire him. Firing Poh Lee Guan when it's time to fire him. They appear to be humble (although the same is not apparently true for the rank and file).
You lose these two things, it will be a bit like the PAP losing its capacity to take care of the lower class people, and losing its reputation for integrity and not being greedy. It can only go downhill.
I acknowledge what you said. Generally, to conclude, I still think there is nothing wrong to suggest that WP leads a coalition, if it is willing, the rest of the opposition camp has to concede.