Firstly, your statement about Percival's lack of combat experience is entirely inaccurate. While it's true he had no combat experience leading large-scale formations, he had a lot of combat experience, as evidenced by the award of MC, DSO+Bar for his service during the First World War. During that War, he rose to become a battalion commander and temporarily took over his brigade in May 1918. His first DSO was awarded during the German Spring Offensive of 1918 where he led a counter-attack that saved a French artillery unit from capture (the French Government awarded him the Croix de Guerre for this action).
Following the Armistice, Percival volunteered for service in Russia, where he earned his second DSO. His citation reads "He commanded the Gorodok column on 9–10 August 1919, with great gallantry and skill, and owing to the success of this column the forces on the right bank of the Dvina were able to capture all its objectives. During the enemy counter-attack from
Selmenga on Gorodok he handled his men excellently. The enemy were repulsed with great loss, leaving 400 prisoners in our hands."
During WW2, Percival was a Brigadier in the HQ staff of I Corps as part of the BEF in France. While he didn't have actual command, he would have been intimately involved in planning and organizing the Corps for operations during the Phony War. This is not "admin work"
Your comment about "home guard" implies some association with the Home Guard, which may be inadvertent...but is equally wrong. He led the 44th (Home Counties) Division which had been part of the BEF in France and was reformed under Percival's leadership after the retreat from Dunkirk. Yes, the Division was charged with homeland defence but that's a very different proposition from the Home Guard.
One other point that needs to be acknowledged is the overall challenge of resourcing Far East Command Command when it wasn't an actual combat zone. We've acknowledged in other threads that Malaya/Singapore/Burma fell well down the pecking order when it came to allocation of resources. That problems is as true for personnel as it is for equipment. Bear in mind that there weren't actually that many general officers with recent combat experience, and those that were around, like Slim and Wavell, were actually doing the fighting during 1941. Pulling them to lead a backwater like Malaya is inconceivable because, in order to have any impact, they would have to be appointed in late 1940 or early 1941 at the absolute latest. Percival himself acknowledged this challenge. If the Japanese didn't attack, then Singapore was nothing more than a non-operational backwater and a career dead-end. However, if the Japanese did attack, then it was unlikely that Far East Command would have the resources to successfully defend the peninsula.
One final note about combat experience. Bear in mind that Norman Schwarzkopf, the Allied commander during Desert Storm, didn't actually have much combat experience. Yes, he had 2 tours in Vietnam, which totaled about 18 months in-country, and he also was put in charge of the invasion of Grenada at the last minute. However, the parallels with Percival are rather interesting. Most of his combat experience, like Percival's, took place when he was a relatively junior officer some 20 years before he assumed large-scale command during combat. Also, Schwarzkopf's experience in Vietnam was far from an ideal preparation for Desert Storm, just as Percival's experience in WW1 may not have been the best preparation for senior leadership in WW2. Percival did, however, spend at least 3 full years in combat-related roles during WW1, then went on to operational service in Russia before taking on an anti-terrorism role in Ireland between the wars. Compared to many generals, that's not a bad record of combat experience.