LeeRoth wrote on 03/08/18 at 01:34:29:
I tried something like this when I was first switching from 1.e4 to 1.d4. After 1.Nf3, I didn’t see 1..c5 very often, and when I did it was usually because Black was a true Sicilian fanatic. After a few of those games, I started questioning the wisdom of allowing these maniacs to play their favorite defense, rather than forcing them to play a d4 defense they may not have studied as much.
So I switched to 1.d4/2.Nf3. My main issues were with the Benoni and KID. I played a Bf4 system against the Benoni and the Makaganov against the Kings Indian. One of the main reasons I later switched to 1.d4/2.c4 was to be able to play the Flick-Knife and Sämisch. I also wanted to play the Nge2 Exchange vs the QGD.
In moving to 1.d4/2.c4, I was also influenced by a friend who questioned why I was trying to avoid things like the Albin and the Budapest, rather than inviting them.
The main downside in moving to 1.d4/2.c4 turned out to be the Benko, which was very popular at the time. I generally played the main, accepted line, but on days I didn’t feel up to the pressure, I trotted out 4.Nf3.
I am currently switching back from 1.d4 to 1.e4, though without giving up 1.d4 completely, and it has been really tough due to my desire and stubborness to play challenging mainlines! I guess my idea is therefore to be able to focus on, say, the Sicilian while not having to worry about the French and Caro for now, but if few players actually play 1...c5, then I won't be able to put my study into practice... I guess I will try it online and see what happens.
I agree with you via the KID/Benoni problem. The best and most interesting lines seem to involve an early movement of the f-pawn. Maybe if I know my opponent well enough to know his/her repertoire, I will just play 1.d4 when expecting such a response.
I am okay against the Albin, Budapest, and Benko, but being able to just not worry about them might be an added bonus against some players. It is really the QGA that gives me some trouble if I cannot remember the sharp lines during the game (I play 3.e4).
Above all, though, I really want to play Open Sicilians with both colours. I have a good feel for them, and love the attacks and counter-attacks that come about, win or lose. It is strange, perhaps, but I feel like 1.d4 suits me better with the exception of the Open Sicilian.
Perhaps there is something to be said for walking around the tournament hall during the opening phase to see what potential opponents are playing, so that one knows whether to play 1.e4 or 1.d4 against them.