On carrots, I think there must be "something to gain or lose" at
the constituency level, or else it makes no sense to vote by
constituencies. And I do think there is reason to have
constituencies... so that MPs can reach out more readily to the
people, and be more focused in doing so.
But should lift upgrading be the carrot? I somehow feel that there
are carrots that should be given out impartially (in which case
they no longer remain carrots... but that's separate issue),
especially those given out by stat boards and government ministries
directly, such as lift upgrading.
Within a constituency, the voted in political party may then
compete on fair grounds against other constituencies and political
parties... using the resources they can gather (perhaps by
adjusting conservancy fees, fund raising activities, etc.) and
provide upgrades / improvements to the areas specific to within
that constituency (including lift upgrading if they want, but that
decision should not be due to "HDB did not approve our application,
because we are SDA not PAP", but perhaps because they simply want
to do more for the people).