Updated from 10:31 a.m. EDTSumner Redstone's move to seize control of Midway Games ( MWY) may end up rattling the entire video-game software industry. Since November, Redstone has more than doubled his stake in Midway; a regulatory filing posted Monday revealed he now holds 71% of the company's shares. The Viacom ( VIA.B) CEO has already nominated two director candidates and could ultimately handpick the successor to Midway Chairman Neil Nicastro, who announced his resignation Friday. Though Redstone has denied it, some analysts believe his takeover of Midway is an attempt to get Viacom into the video-game software industry, which could have far-reaching implications. In a narrow sense, Redstone's wheeling and dealing would most directly affect Activision ( ATVI), which has developed games based on Viacom's movie and television properties, and, more significantly, THQ ( THQI). Of the $640.8 million in revenue that THQ posted last year, analysts estimate that 15% to 25% came from its Viacom titles. If Viacom absorbs Midway, "the big risk is on THQ," said one fund manager, who has no position in THQ or Midway. More broadly, the media mogul's Midway moves could touch off a bidding war by rival entertainment companies for the other video-game makers. "I think they're in play," said Michael Pachter, who covers the video-game software industry for Wedbush Morgan. Entertainment companies "are all copycats. If one guy buys a TV network, the other one has to buy one, too." (Wedbush Morgan has no banking business with Midway or the other major video-game companies; Pachter does not hold shares in the companies he covers.) Other video-game stocks may well benefit if Redstone rolls Midway into Viacom, or if Viacom makes other purchases in the sector. Such a move would "set a precedent" of a big entertainment company buying its way into the video-game publishing business, said Pachter.