Yes, please:
1.) bring back multi country origin

2.) could we change the format from:
+cabin 1 --> +cabin first or as in GDS --> kf
+cabin 2 --> +cabin biz or as in GDS --> kc
+cabin 3 --> +cabin eco or as in GDS --> ky
+cabin premium coach --> +cabin premeco or as in GDS --> kw

3.)
could we add searching multi cabin (mixed searchesfor outbound and inbound flights?
i.e.
01DEC HAM-NYC Prem Eco
10DEC NYC-HAM Biz
as of right now this is not possible, even with +cabin since +cabin is a must then on all segments, and when you have a connecting flight, i.e. HAM-FRA-NYC where no Prem Eco is available on HAM-FRA this will not show any results

4.)
higher timeout
ofc lower timeout is required to keep down the costs, a paid version in the price range of AMA Masterpricer / Sabre Bargain Finder Max could be possible

5.)
maybe change the booking class request format?
currently bc=Y | bc=W | bc=...
--->
either as in GDS:
/cy,w,...
or just short
bcy,w,...

6.)
make "add advanced controls" sticky, maybe as a cookie?, so we don't have to click on it every time again for each search