On Fr Hunwicke's Liturgical Notes there is a very good posting on what we may do with Ad orientem celebration. Ad orientem is a practice that I fully support.
The question has come up in a few places that I have served at.
For the feast Day of San Josemaria we celebrated in a church in Brisbane which has a fine High Altar and a stone freestanding table Altar in front of it. However, the congregation faces directly westward. The last 2 solemn Masses I MC'd there we had the Liturgy of the Eucharist celebrated on the freestanding Altar, with this Altar decorated with an Altar Cross and 4 candles, with the High Altar having the full six tall candles lit. It looked very nice.
A friend suggested that we should celebrate Ad Orientem. Fine I say, but the priest is then NOT looking East towards the rising sun streaming in through the East doors but a wall facing West. The other thing is that if the priest celebrates facing West (oriented towards a liturgical "East") does he celebrate at the freestandig table or the old High Altar? My thinking is that he should celebrate at the High Altar.,as celebrating at a table at the foot of the High Altar would look silly. This presents another problem. In the Modern Roman Rite, the Offertory prayers and the Eucharistic Prayer are celebrated aloud to be intelligible to the congregation so rightfully the High Altar should be miked which it isnt. Therefore until the technological barriers are overcome, the best solution is to continue to celebrate at the table Altar (properly decorated with a central cross) facing East.
I have a similar problem at another church. This one is of a traditional Roman Basilica plan and with the front door facing North East and the apse facing South West. It has a freestanding stone Altar only, but with a giant wooden crucifix at the centre of the apse. As much as I would like to get the priest to celebrate Ad Orientem, this also present difficulties. Should I arrange the Altar to have the priest facing the cross, but keeping him facing SouthWest, or having him face towards the East but with the cross behind him? The Altar is decorated with four candlesticks and a central Altar Cross (I used to have 6 but I find on many Altars they are simply too small and the Altar then gets crowded by candles which take away from the central aspect of the Altar as the resting place for the Body and Blood of Christ - 4 is often a good balance).
For the moment I have kept it to having the priest facing East (actually North East), and I am of an open mind to get him to face the other way (if a priest is indeed amenable and sufficiently educated liturgically to understand what he is doing), but I am keen to have a Modern rite Mass to see what the feel of an oriented liturgy with the priest and congregation face the same direction actually is like.