Replace tie with slur, non-destructive

[Nils]

Hello,

this is a bit annoying, but I have to ask it nonetheless.

After a lengthy discussion with my publisher about the shape of ties I 
mentioned as final statement: "But this way they become indistinguishable from 
slurs!" and he said "Yes, this is exactly how it should be!".
I am the one with the better reasons but he is the one with the money.  I 
refuse to change all my ties to slurs destructively and forever in my lilypond 
sources. I want to keep the correct form for later. Not to speak of the amount 
of work doing this for around 60 pages.

Can I trick Lilypond into generating a slur when I say "tie!" ?

Nils