I think at any resort you could request a private dive guide each if they have enough on staff. Why not just ask.
In Lembeh, typically the boat will come get the divers, so with solo divers there may be a concern that you will surface someplace far away from where you had gone in.
Also besides the diver to guide ratio, ask the resort their policy on length of dives. Some let you dive to the limit of your air/abilities and others have strict and some not so strict one hour time limits.
In Lembeh you are always better off with a guide. The lower the diver to guide ratio the better, especially for photographers. Paying extra for a private guide will be a lot cheaper than going to a more expensive resort. As a percentage of overall cost of your trip paying for private guides is a tiny increase.
An expensive resort does NOT necessarily have the best guides. Also some guides are better at finding certain things than others. Though I have found all the guides good and always willing to look hard for those special things you want to see. Tell the guide what you are interested in.
Bring a good Critter ID book, as the guides may not always know the critters by the same names you do, or understand the taxonomy that separates Nudibranchs from their cousins the Pleurobranchs (you will see large ones at night, eight or ten inches long) and they may call them all Nudibranchs.
I highly recommend Reef Fish Identification - Tropical Pacific by Gerald Allen Roger Steene, Paul Humann, Ned DeLoach (you can get it for about US$30 including ground shipping from Amazon now) Some of the photos were taken in Lembeh, so you may spot the descendants of the fish in the photos.
The guides will be happy to go thru the books with you after the dive and point out what you saw. They will also be interested to learn what you can teach about taxonomy and critter behavior.
My guide Risko from Two Fish Divers has a knack for finding pygmy seahorses. Off Bangka Island he found a small Gorgonian sea fan about the size of a ping pong paddle with TEN pygmy seahorses. I think he was more excited than I was. That's when you know you have a good dive, when the guide is having as good or better time than you. Opo, the resident guide at Two Fish Divers, Lembeh has done over 9.000 dives. Maruf at Two Fish on Bunaken has been guiding for over twenty years.
I also try and bring something for the guides or leave them with some gear (snaps, links, magnifying glass, backpacks, etc) They all are very enthusiastic and proud of their underwater backyards.
I also ask the resort manager/owner if there is any last minute thing, small and special they need from abroad, sometimes its a battery for a camera or dive computer, the latest memory card for cameras or the download of a camera manual off the internet (the Internet is a lot slower in Manado area than in the US or Europe) or bulb for an underwater light. I try and make a CD with music for the office staff. I give spare rope and cotton garden/work gloves to the boatmen.