In May 1940 the Fokker G1 surely was the best plane the Dutch airforce could offer. Generally speaking in 1940 the Fokker G1 was not bad plane but as soon would appear in combat with other fighter planes it was not a good match.
The G1 in its time had a very progressive concept. This concept is now known as the multirole fighter. Basically a fighter which must be capable to perform all tasks but is not excellent at any task. (JSF Joint Strike Fighter / Tornado).
Quote from the Fokker G1 Mercury manual :
The Fokker G1 is a 2 or 3persons fighter, designed as two engine cantilever midplane , suitable for different functions , such as :
 GROUND ATTACK AIRCRAFT
 WARPLANE/FIGHTER
 BOMBER
 DIVE BOMBER
 RECONNAISANCE
The idea to develop this type of multi role fighter was an idea from Fokker himself, however the idea of a multi role machine was already known.
Around 1936 other aircraft manufacturers around the world developed aircraft with similar specifications. The best known is the Messerschmit Bf 110 Zerstorer . This multifunctional idea lived in several countries , as is demonstrated by the strong interest and sales of licensed construction of the G1 abroad. (Spain, Denmark , Sweden) Although the specifications for the G1 Mercury were drawn up by the Air Force implementation was largely owned by Fokker. The requirement to serve as a reconnaisanceplane meant that the G1 had to have a reasonable range, an observer and radioman to signal through the observations.The view had to be good hence the many windows in the hull (in practice the pilot proved to have the best view). The radio equipment at that time was quite heavy (69 kilos). All this together resulting in a rather large airplane. (hence likely to be called "G1")
The pilot was obviously in the front, behind him between the main beams the radio operator, and in the shooting dome the observer / gunner / bombardier . The intention was that the G1 was flown to a 3man crew while observing and in other roles with a 2man crew.
General information (from official manuals). For comparison, also the data of the Fokker G1 Wasp is shown:
MERCURY 
WASP 

Flight 
17.16 meter 
16.50 meter 
Lenght 
10.87 meter 
10.38 meter 
Height 
3.80 meter 
3.35 meter 
Gauge 
4.63 meter 
4.00 meter 
Wing area 
38.30 meter2 
35.70 meter2 
Wingload 
125 kg/m2 
123 kg/m2 
HPload 
2.90 kg/hp 
2.95 kg/hp 
Range 
1500 km cruising at 4265 meter altitude at 383 km/h 
1450 km cruising at 3400 meter altitude at 355 km/h 
Engines 
Bristol Mercury VIII 9 cilinder star volume 24.9 liter 830 HP / 4100 meter 
Pratt & Whitney Twin Wasp Jr SB 4G 14 cilinder double row star volume 25.1 liter 825 HP / 0 meter 750 HP / 2850 meter 
MERCURY  WASP  
plane composition 
2 persons  3 persons  2 persons 
empty weight 
3330 kg  3345 kg  3150 kg 
load 
1470 kg  1455 kg  1250 kg 
Total weight 
4800 kg  4800 kg  4400 kg 
Maximum allowed weight 
5000 kg  5000 kg  4800 kg 
Speed
Altitude 
MERCURY  WASP 
0 meter 
399 km/h  384 km/h 
1000 meter 
417 km/h  400 km/h 
2000 meter 
436 km/h  418 km/h 
4000 meter 
473 km/h  439 km/h 
6000 meter 
452 km/h  421 km/h 
7000 meter 
435 km/h  412 km/h 
Climb rate
MERCURY  WASP  
Altitude / weight 
4500 kg  5500 kg  4400 kg  4800 kg 
0 meter 
13.9 m/sec  13.3 m/sec  12.3 m/sec  11.2 m/sec 
1000 meter 
13.9 m/sec 
13.3 m/sec 
11.1 m/sec 
10.0 m/sec 
2000 meter 
13.9 m/sec 
13.3 m/sec 
10.6 m/sec 
9.5 m/sec 
4000 meter 
12.2 m/sec 
11.6 m/sec 
8.5 m/sec 
7.3 m/sec 
6000 meter 
8.1 m/sec 
7.6 m/sec 
6.6 m/sec 
5.5 m/sec 
7000 meter 
6.1 m/sec  5.7 m/sec  4.6 m/sec  3.6 m/sec 
9000 meter 
2.2 m/sec  1.9 m/sec 
Maximum altitude
MERCURY  WASP  
4500 kg 
absolute 10150 meter in practice 9900 meter 
4400 kg 
absolute 9300 meter in practice 9000 meter 
5000 kg 
absolute 10000 meter in practice 9750 meter 
4800 kg 
absolute 8900 meter in practice 8600 meter 