I am fine with a "beta" period of time.
I would like to have the invasion of the Inner Sphere start aroun the canon timeframe and then develope more freely;
the events should not really follow lore, especially planet conquests, however it would be cool to play the famous battles of the lore. They have already mentioned special events with faction-based restrictions.
For example, when Clan Jade Falcon conquers a planet within 1 jump from Twicross, an event is triggered: the battle of Twycross. A small tournament might be cool, but i would leave the details of the event to PGI (i would say a sale of CJF colors would be fitting too - sales will never end, if nothing else they should be lore-based

). Small prizes could be awarded.
There are two issues however. The main battle of Clan Wolf and Clan Smoke Jaguar (not counting Tukayyid) were attacks to capital worlds (Rasalhague and Luthien).
Possible solution 1: no one can capture capital worlds. Even if the Clan wins," strong revolts and guerrilla warfare from remntants of the planet's defenders" will force the Clan offworld. Basically, even if the Clan wins, they will not take the planet. This is the easiest but obviously not my favorite solution.
Possible solution 2: capital planets can be captured,with some disadvantages for the losing faction but not meaning their defeat. After all, the royal family can escape off world and coordinate the war from a close important planets.
Such a faction would offer very rewarding contracts for merc units willing to fight to retake it (in case of victory), and similar bonuses for regular units of that faction. This, in my opinion, will be enough to press the players into retaking their beloved capital world

(see how many people are worried about c-bills grind in CW..).
The other issue? I do not recall any important battle (before Tukayyid) for the Ghost Bears to play in

Any ideas?
For these battles, i think it would be cool to have both a regular planetary conquest queque (with 'Mech restrictions though) and a 'Mech restricted small tournament or skirmishes hosted by NGNG.
Example: battle of Luthien.
The event could last any long from 3 days to a week (but not too much). Planetary conquest may be decided by the standard planetary assault (in case of solution #2) In the meanwhile, a special event is hosted by NGNG: a number of Draconis Combine, Wolf's Dragoons and Kell Hound player units would be invited and put against an equal (or lower: bidding!) number of Smoke Jag and Nova Cat units (Go Pariah Devalis!). 'Mechs would be restricted based on the most present 'Mechs in the two Clans' toumans and on the 'Mechs manufactered by Combine factories. It would be the perfect time to introduce the Cauldron-Born, too!
Small MC prizes would be awarded to the partecipants.
A note for Tukayyid: i am not quite sure if we should have a battle of Tukayyid for the ownership of Terra (how can the Clans decide which one is going to be the IlClan?
Inter-Clan Trials maybe?) or just the Clan that gets first within 1 jump of Terra vs the defenders.
Anyway, in its special event, the defenders should be any ComStar player unit and possibly mercs (ComStar can hand mercs some good rewards!) vs an equal or lower number of units of the Clan/Clans.